Minecraft Wiki:Issues

This page's purpose is to list all the bugs players have come across. Most of the single-player bugs also apply to multi-player. Version history also contains bugs that aren't listed on this page.

Bugs and feature requests can now be logged at Getsatisfaction: Mojang.

General

 * If the FPS is too low, Minecraft will close without saving any chunks. The inventory, player position, momentum, and time will all be maintained, however, as these are stored in the level.dat and are constantly updated.
 * If Minecraft crashes, your world may revert back to an older save from the last time you saved & quit.
 * Occasionally, the level.dat file is re-written, causing you to lose your held items, and generate a new spawn. Also occurs in SMP.
 * You are unable to directly swap items in your inventory if the two items are same. This is important if you would like to swap the same item type with two different durability values. This is a result of the way combining stacks works.
 * Sometimes you can see through everything; this randomly happens on all games on all platforms. Toggling the fog distance will change everything back to normal (Default key is F).
 * When you open up the achievements interface at night, wherever in the sky there is not a cloud, the sky will be white.
 * While viewing the achievements interface, the world is not paused. Everything can move, as if opening the inventory.
 * Occasionally, picked up items will not appear in the inventory.
 * Sometimes, the game may reset the seed that the map generates from. This is a result of tweaks of the seed and terrain generation code that are regular parts of the game's updates.
 * Sneaking prevents movement from Soul Sand or Cacti to any other block.
 * If you are sneaking when you exit the game, when you reload the game you fall into the block below you, and onto the block below it instead.
 * The red glow featured at sunset and sunrise is normally a gradient. Pulling up the player's inventory will cause the gradient to solidify along a sharp boundary.
 * If you hold the left mouse button down while holding a item, then open your inventory, still holding the left mouse button, and then close your inventory, as long as you don't release the left mouse button, you are able to break blocks without the swinging item animation.
 * Occasionally, when saving the game and reloading, you will fall through the block you were standing on. This can be prevented by jumping as soon as the game loads.
 * A bug exists where the game may refuse to remember custom controls after updating (not to a specific version - just updating in general). This is caused by one of the values in Minecraft's "options.txt" file being unset, usually the "lastServer" field - attempting to connect to any multi-player server address (valid or otherwise) typically resolves the problem.
 * Occasionally, some chunks of the map do not update with the day/night cycle, as seen here. Also, even in caves or closed environments the player can still see lighting bugs, (i.e. An area has full light and it has a small spot of full darkness next to it. When the spot is edited, it changes to normal.) These glitches are fairly common and can cause multiple problems. Usually staring in the general direction of the chunk for a moment will fix this.
 * If you enter Fullscreen mode, then exit it, mouse clicks will no longer work for game dialogs (game menu, inventory etc.). However, mining and using items still work. Pressing Esc, waiting for the game to save and restarting the client or re-entering fullscreen to save and quit resolves this problem. Here is a topic on Minecraft Forums related to this bug.
 * If you hit a movement key and at the same time open inventory or click that movement key will become "stuck". Pressing and releasing the same movement key again will stop you again.
 * If you disconnect from a server while a message is displayed, and then load a single player world, the text will appear in SSP as shown here.
 * Sometimes mobs within a certain area will stop moving, and entering the area will cause the player to become rooted to the spot and often vibrate wildly. Many animations, such as digging and health recovery will be broken, and mobs that the player hits will constantly loop the damage animation without dying.  It is not possible to catch fire.
 * If the player adjusts their system clock one hour forward, the game will run abnormally fast, allowing quick movement and mining. Changing the time back, exiting the game, setting the time forward again, and re-entering the game will allow you to change the system clock properly. Note that the inverse of this is not true--setting the time backwards will not slow down the game.
 * The openAL32.dll and openAL64.dll that come with Minecraft do not work properly. This sometimes causes Minecraft to crash when players turn sound on in the options menu. On Windows machines, deleting Minecraft's openAL files usually solves the problem, because Minecraft will then automatically use Windows operating system's copy of the openAL dll, which works properly.
 * Selection bounding box breaks ATI card's Anti-aliasing.
 * Sometimes Smooth Lighting doesn't work properly in water
 * Smooth Lighting acts weird on certain blocks like signs, doors, and other special blocks
 * The hat layer in a player's skin is in an incorrect position when sneaking.
 * The Tab key is unresponsive unless the game is in fullscreen mode.

Arrows

 * Arrows that hit doors can float if the door changes its state.
 * They also appear to collide with fences, portals, and sugar cane. Arrowsugarcane.pngArrowportal.png
 * Arrows that have not hit a mob become unobtainable if you die or save and quit then begin playing before retrieving them.
 * Tilling dirt with an arrow on it will cause the arrow to fall through into the next block.
 * Arrows that hit a Minecart become unobtainable, similar to arrows damaging a NPC.

Beds

 * While sleeping, particles (torches, furnaces, etc.) do not "adjust" to face you, some of them may look flat or even be invisible.
 * Beds placed in fully enclosed (on both sides and with only one space above) areas can cause you to wake up inside a wall, killing you and potentially destroying your items.
 * Beds cannot be placed on snow.
 * Putting a Powered Rail in the front of your bed will make it so when you wake up it will still be night, as if you never went to sleep. (Only tested with the powered rail on)
 * Depending on the placement of a bed monsters will spawn on or near the bed regardless of light level. Sometimes this can occur even if the bed isn't touching any walls. This can also occur in SMP.
 * If the player right-clicks the bed fast enough, they will recieve a message saying: "This bed is occupied" even though they are on SSP. this is caused by the last click to attempt to get in bed being performed during the game placing the player in bed, tricking the game into thinking someone is already there.
 * Temporary fixes for mobs inexplicably attacking during sleep include: having at least 5 spaces between the bed an the nearest wall, having door on the same level as the surrounding (outside) ground and replacing the floor with glass.
 * Beds being broken appear to get brighter
 * If you place a bed on the highest level of the map, it will be lost
 * If a room has a low ceiling, you will suffocate once leaving the bed.
 * You can sleep during a thunderstorm, even during the day

Boats

 * Boats will collide with a snow layer as if it is a full block when placed on land.
 * If you manage to stand on your boat while it is under water, the boat will be unable to rise. The boat will still retain horizontal movement, though, and will often slide out from underneath you.
 * If you go under a water stream your boat will accelerate and rise upwards. This is an error in the programming of how boats float.
 * If you save and reload while in a boat, you will no longer be in the boat.
 * Pressing F5 whilst in a boat will show your leg/foot armor protruding from the bottom of the boat, even though your character is sitting. The leg armor will also fail to properly adjust to still be around the player's legs and will still be going straight down as if the player was standing still.
 * If you place a boat on the ground and drop sand onto it, the sand will repeat the falling animation on the top of the boat and you will be able to pass through it. Reloading the world will properly place the sand, but the boat may be dark as if it's in an area with no light.
 * Exiting a boat will sometimes make the player to fall through it. This could be fixed by implementing code that would place the player one block higher than the boat when it's exited.
 * If an occupied boat crashes into an unoccupied one, only the occupied one breaks.
 * If you enter a portal while in a boat, Minecraft will crash
 * Boats, like many objects, are invisible at the top layer of the map

Cactus

 * Cactus also has a South/West rule for applying damage. Placing a block above a single cactus piece prevents you from stepping on the cactus and prevents you from taking damage by pushing against the south or west sides of the cactus. The north and east sides of the cactus can still hurt you.
 * If a door is placed next to a raised cactus, both will break, but 2 doors will be dropped.
 * If a door is placed level with the cactus it will break the cactus and the bottom part of the door, leaving a un-collectible but breakable window.

Dispensers

 * Unlike chests, when a dispenser is destroyed, the items inside are gone forever. Notch stated that this is a bug on Twitter.

Doors

 * If you place a door next to a Cactus it will break and drop them both, but the door will drop two doors instead of one as shown Here. This can be reproduced indefinitely.
 * If a door is placed level with the cactus it will break the cactus and the bottom part of the door, leaving a un-collectible but breakable window.
 * 'Double doors' do not open simultaneously as one might expect them to when activated with redstone.

Fences

 * Occasionally, placed fences will become invisible under certain conditions: if there are no actual blocks within a pre-defined 16-block-high layer of a chunk, any fences placed within will be invisible.

Fire

 * Fire has a South/West rule for applying damage. Placing a block directly above a fire prevents you from stepping into the fire and also makes it impossible to damage yourself by pressing against the block from the south or west sides. The north and east sides of the fire can still hurt you.
 * It is possible to have "Invisible Fire", fire that is dark and unlit.
 * A forest fire can cause strange patches of light to be left after all the fire has burnt out.
 * If a block is placed directly above a burning netherrack, or any fire, and water is placed on that, it will constantly emit a hissing sound. Can be used to annoy players on SMP.

Furnaces

 * When destroying a Furnace, unlike Chests, anything inside the Furnace will be permanently destroyed.
 * Furnaces emit light even if its face side is blocked. This is because the block itself emits the light, and it could be fixed by making the block in front of it emit light instead.
 * When you put coal + a smelting item in a furnace, then leave and re-enter the world, the fire icon glitches and will not shrink until the fuel source is about to run out.

Glass

 * Glass placed in the same block as an item entity will not displace said item.
 * When water is above glass, source blocks are never created.
 * If you attempt to light glass on fire, the durability is lowered without any flames appearing
 * Placing glass on top of a chest does not prevent it from being opened
 * Clouds seen through glass disappear during the breaking animation
 * Glass placed next to downward-flowing water appears to increase the force
 * When standing under glass during rain, the outside ambience for rain plays. Also, dogs play the shaking animation while under glass.
 * If a glass wall is placed next to TNT in water and you stand on the other side of the glass, you will always take only a half heart of damage.

Grass

 * Grass does not grow under signs or fences.
 * It appears that in arctic biomes, next to ice, grass can be generated underwater by the terrain generator.
 * When hacked into the inventory, the texture for grass blocks is rotated sideways
 * Grass does not disappear if stairs or glass is placed on top

Gravel or Sand

 * Gravel or sand will not fall down if a non-solid block is placed between the time a block underneath is destroyed and before the sand/gravel begins to fall. Example
 * Gravel or sand will accumulate into resources if a non-solid block is placed between the time a block underneath is destroyed and during the time the sand/gravel is falling to fill in the spot. Example
 * If you break a block below gravel or sand and are walking into gravel or sand, you will literally walk into the gravel or sand.
 * If you allow sand or gravel to fall on you, after moving around it is possible to be in such a position that you will not suffocate and you will be able to see through the sand or gravel and any blocks connected to the sand or gravel. This can reveal caverns.
 * If you place a sand or gravel block then quit the game before it starts falling, upon reload, it will float. If a nearby block updates, it will fall.
 * When sand or gravel is generated above a cave (or any opening), it will float until a space by it is modified in any way.
 * When sand or gravel is put above a boat, it will fall forever and act as "Quicksand"

Ice

 * Items dropped in water flowing over Ice move much faster than normal
 * After the Beta 1.5_01 update, Ice no longer regenerates when it is snowing.

Ladder

 * Ladders create a 1x1 air bubble around them, allowing you to breathe underwater
 * Ladders can prevent liquids from flowing into an area
 * If a liquid flows over a Ladder, it will be suspended in midair. It does not flow downwards.
 * Spiders can not climb a wall if a ladder is placed on the wall.

Lava

 * Sometimes lava won't cause damage. More common in SMP.
 * If the player moves into a corner to their southwest of which lava is on the other side, the player will be damaged(see South/West rule). This same bug can also incinerate items and other entities.

Levers

 * Levers can be placed on the bottom of a block, as long as there is an open space, and a block horizontal to the open space. The lever will act as if placed on the horizontal block, but looks glitched, as shown [[Media:Brokenlever.png|here]].
 * Placing a lever on snow or glass will produce a similar effect.
 * Levers placed on slabs have a glitched model.
 * Levers placed horizontally and facing North/South will not deliver power to surrounding blocks properly, whereas levers facing East/West will. With N/S levers power is only supplied to the four blocks on the same level as the lever and touching it. With E/W levers the four blocks level with and touching the block below the lever, and the block below that block, will also be powered.

Lightning

 * When striking, ice, water, portals, rain, snow, and other particles behind it become see through.
 * You can sleep in a bed during a thunderstorm, even during the day.

Minecarts

 * When spawning mine carts on a small track, they will gain momentum from colliding with each other.
 * Riding a minecart at the top of the map makes the player invisible until you leave the cart or ride downwards.
 * Sometimes minecarts disappear completely for no reason.
 * Riding a minecart into a Nether portal causes the game to crash and kills the player.
 * Removing a minecart while riding in it will cause the player to go through the ground.
 * Minecarts can go off tracks or crash through the ground if their momentum is too high.
 * When exiting a minecart, if there is only a single block free above the track, the player will take some damage.
 * If you start sneaking right after destroying a minecart, you may crash and get buried, but there is also a chance you will get multiple minecart drops.
 * When exiting Minecarts when there is a block in front, the user may rarely glitch into the block directly underneath the Minecart and appear to be walking inside of that one block with the upper torso the only part showing until the user jumps out of the block.
 * If TNT is detonated near a minecart, it occasionally drops more than 1 minecart.
 * You can ride a saddled pig that is in a minecart
 * If 2 minecarts are put in a circular track, they will constantly bump into each other, accelerating. Very laggy in SMP.
 * A player/mob can be in a flaming minecart without taking damage or being set on fire themselves.
 * Water does not put out burning minecarts
 * If 2 minecarts on side-by-side tracks collide at an angle, they will both accelerate until they become disconnected.
 * If a minecart is dropped directly on top of another, they will combine into 1 cart, and accelerate twice as fast in a booster. More carts can be added for stronger boosting power.

Mobs

 * If a mob is riding a minecart and 2 or more mine carts get stuck in each other, after destroying or moving the carts away from the other carts the mobs will be invisible.
 * When up close to a Zombie Pigman, the inventory GUI will become much brighter. This could be interpreted as a "hint" towards future trading/interaction with some mobs.
 * If you are above a Ghast's height and are standing still, Ghasts will shoot fireballs over your head, without damaging you.
 * Ghasts will shoot at the camera in 3rd person view.
 * Squid can spawn in unintended locations, such as from cavern springs or even in The Nether(if water is hacked in). This is more common in multiplayer.
 * Mobs can move briefly before map data is loaded when signing out and loading the world, usually resulting in the mobs getting stuck.
 * Tamed Wolves will attack you if you shoot yourself with an arrow. This can be achieved by looking straight up, shooting an arrow, and moving forward a small bit to compensate for a small amount of curve.
 * If a wolf is tamed when it's attacking another mob, it may still attack it when on sitting animation.
 * Creepers will sometimes 'remember' the burning of their fuse, and detonate immediately if approached again.
 * If you are riding a pig, and it walks into a low room, you may start suffocating.

Paintings

 * Paintings can be placed inside snow.
 * Paintings can be placed co-existentially inside water.
 * If a painting is placed on a block with a fence on top, the painting may be 1x2 in size. This can not be removed without breaking the block or fence.
 * A broken painting will rarely drop 2 paintings.
 * A painting placed over a light source does not block the light.
 * Paintings do not use the smooth lighting, even if all blocks around it do.
 * Objects can be placed in larger paintings.

Portals

 * Placing a boat in the portal and entering it will cause the game to crash.
 * Similarly, riding a minecart or a pig into a Nether portal will cause the game to crash.
 * Being killed in the Nether will cause chunks and a portal to be generated near your relative location on Earth, as though you had teleported back from the location at which you died normally.
 * Dying while in the Nether will also ignore a changed spawn point (via sleeping).
 * Opening the inventory then crafting while in a portal will destroy the item you are crafting and make the loading screen text turn gray, will add an identically gray "shadow" beneath the text, and will prevent the loading bar from filling. Everything will load as normal, though.
 * If the game is closed while entering The Nether, you will be sent to your spawn point on earth without held items, as if you were killed. However, it ignores a when the player's spawnpoint is changed via sleeping.

Redstone Repeaters

 * A repeater will freeze upon save and reload of a world.
 * The particle effect while destroying a repeater are the same as pumpkins.

Sapling

 * If snow, fire, water, or lava are over a block, a sapling may be placed on that block even if it is not a dirt block. After a short time the sapling will recognize that it is illegally planted and uproot itself.
 * If flowing water hits a sapling, the item won't be dropped
 * A tree can grow on top of a player, suffocating them
 * If a sapling is planted at the top of the map, it will grow into a single wood block

Sign

 * Placing a sign on top of a block at the maximum height removes the item from your inventory without creating a sign.
 * You can place signs on top of other signs.
 * Signs create a 1x1 air bubble around them, allowing you to breathe underwater.
 * Signs can prevent liquids from flowing into an area.
 * If a liquid flows over a sign, it will be suspended in midair. It does not flow downwards.

Sugar Cane



 * If a block is covered in snow, fire, water, or lava, sugar cane can be placed on that block violating the usual placement rules for sugar cane. When the sugar cane grows it will recognize that it is illegally planted and uproot itself leaving two loose sugar cane blocks.
 * Bugs in the terrain generation code can cause Sugar Cane to float.
 * Sugar cane creates a 1x1 air bubble around it, and can be used to breathe underwater.
 * Ghasts can not see you through sugar cane
 * Arrows do not pass through Sugar Cane
 * The actual sugar cane block is still named "Reeds" when hacked into the inventory.

Snow

 * Utilizing snow, one can place saplings, cacti, and sugarcane on any block. However, the cacti and sugarcane will break when they first grow, and the sapling will uproot itself after a while.
 * In snow biomes, water and lava lakes can generate below the snow and leave some of the snow floating.
 * Beds cannot be placed on snow.

Stairs

 * Stairs, along with fences, can sometimes become invisible. Water may be the cause of the bug.
 * When smooth lighting is disabled, the inside faces of stair blocks (those not along the block boundary) will sometimes be improperly lit (usually far darker than the surrounding faces).

Slabs

 * When firing arrows at the opposite corner of the slab, your arrows may clip through and hit the block behind it.
 * Wooden slabs can currently only be properly collected with a pickaxe instead of an axe. This may be caused because all 4 slabs use the same data value.
 * When walking with 50-100% of your body over a slab, whilst being at the high of another block, the walking sound effect for the slab type will play, rather than the one which you are actually on.
 * A player can not walk from soul sand to a slab without jumping
 * A single slab cannot be made into a double slab if there is another solid block directly above the signel slab.
 * If a single slab is placed above a chest, the chest can still be opened
 * If water is placed directly adjacent to a slab, water will not flow on top, and instead appears to create a short water wall.
 * Torches can not be placed on single slabs
 * It is impossible to be suffocated by single slabs
 * With Smooth Lighting on, a slight amount of light can be seen passing through the sides of slabs. This does not affect mob spawning.
 * If a slab is placed on ice, it still has the "slippery" effect
 * If half blocks are placed next to TNT, the damage is significantly reduced



Water

 * Under certain circumstances, underwater players can breathe, and see through the water. An example is shown here.
 * Like lava, when water is touching the same corner as you it has a possibility of colliding with you, allowing you to float upwards. (South-West Rule)
 * Numerous strange objects will prevent the flow of water such as signs, sugar cane, doors, fences and half-blocks.
 * Water sometimes doesn't flow into newly generated areas.
 * Unlike Glass, other water blocks are invisible when viewed through a waterfall, even though there is air in between. Example.
 * Water source blocks do not regenerate over glass
 * Water buckets can not be poured in the Nether, but water blocks can be placed if hacked in.

Workbench

 * If you access a workbench and press the jump key, sneak key or a movement key, your character will act as though that key is still being held even after exiting the workbench's interface. This can be fixed by pressing the same key after leaving the workbench's interface.

Mac OS X

 * On some Mac OS X Systems, the World Select screen will not appear at all, making the game unplayable on those Mac systems.
 * In other cases, the Mojang AB logo will appear green and the title screen and the game in dark areas will appear red.
 * on some Mac OS X systems, when the player is done and ( X'es out of the window ) the computer will take hours to close. The mouse will be able to move, but the windows and anything else will not be available until it closes. And when it does, the top bar on the screen will become black, and hard to see, so, either way, you will have to shut down, or keep the window open forever.
 * Under MacOS X, Minecraft does not respond to either the Quit item in the Minecraft menu or it's shortcut, ⌘Q.

Biomes

 * In worlds generated before Halloween 2010, without biomes, it will snow.
 * If a world was generated before Halloween 2010, the first biome will contain a chunk error, usually near a big mountain.
 * In snow biomes, it will snow underwater if the water is not yet frozen to ice.

General

 * If a player has respawned, he can place blocks on the block he is currently standing on. This will not decrease the block count in his inventory, effectively cloning blocks. This bug only occurs with non-opped players.
 * Full server world saves do not reliably save the entire world. This can be proven on a single person private server with whitelisting enabled when attempting to do a full server save via:
 * 1) Disabling incremental level saving with 'save-off' on on Minecraft console.
 * 2) Forcing a full save to disk with 'save-all' on on Minecraft console.
 * 3) Archiving and saving the archived world with 'tar -xvzf save.tg world' on shell in secondary system console.
 * 4) Turning back on incremental level saving by doing a 'save-on' on Minecraft console.
 * Enormous, cuboid areas (usually one or two chunks) of unfinished map open in random places. Caves, minerals, water, magma and mobs are visible when a Player peers into one of these voids. These areas cannot be walked on, causing a "[user] moved wrongly!" message to appear in the Server; however, players can ride minecarts through them with relative ease. If the void appears in the middle of water, Players can "float" over the void using a boat. Placing a torch next to one of these "void holes", dumping lava or water nearby, or disconnecting and reconnecting to the server will make the land inside of them reappear. These have become significantly less common since the 1.3 update.
 * When you sneak (in third person), your character's feet are "in" the ground.
 * Occasionally, the level.dat file is re-written, causing Minecraft to generate a new spawn. Also occurs in SSP.
 * Seemingly as of Beta 1.3, some players have been getting huge amounts of strange lag. They get good fps, but everything from placing blocks to damaging mobs can take anywhere from 10 seconds to 6 minutes. It is apparently related to the server, and NOT client-sided. The server recieves the data, but takes a long time to send it back out. It appears to only affect 1-2 people at a time, coming and going randomly.
 * As of Beta 1.5, this problem seems to be less severe, but still exists.


 * The minecraft server sends unnecessary many but small network packets. Between packets are often less then 0.00001 seconds. Tests have shown that if those packets get manually buffered that some players will have less lag and less disconnects. See this top 10 getsatisfaction problem report's user solution for more information.

Arrows

 * Arrows shot onto a wall cause the arrow to create a flickering wobbling repeat of the arrows movement. This happens mainly on glass.
 * Fired arrows will appear to come out backwards at first, then continue on a regular trajectory.
 * Many arrows fired appear glitched and stay in mid air, going back and forth, even if they hit a mob or another player.

Beds

 * Sometimes when a player is sleeping and other player walks on that sleeping player the sleeping player will fall through the bed and the floor.
 * Trying to get into bed while sneaking disconnects the player(Illegal Stance).
 * If someone uses their bed in SMP, other players may get disconnected(Unrecognizable Packet ID: 17).
 * Attempting to hoe under a bed that would experience the monster spawning error would kick the player that used the hoe (illegal stance).

Boats

 * If you ride a boat over a chunk of water which did not load properly ( ex. the water is really there, but you can't see it and can see through the whole world ), the boat disappears.
 * When a Boat gets damaged (by a player), it does not shake.
 * If you see a player riding in a boat, it sometimes looks like they are running in the boat, rather than sitting.
 * If you exit a boat, you may get stuck standing on top of the boat. This is similar to how fences used to act.

Dispensers

 * When a dispenser dispenses an item, there is no smoke puff and no sound is heard.

Doors

 * If you open and close a wooden door repetitively while jumping, you can catch yourself in the door and jump again. This can be used to reach places 1 block higher or to get on top of wooden doors overall.

Furnaces

 * Furnaces rotate when they are used. This seems to be influenced by the blocks placed around them.
 * Furnaces can stop smelting items during a severe lag.

Jukeboxes

 * The records duplicate if you eject the record before the song has finished. Only one record can be picked up however, the rest are client-side duplicates.

Ladders

 * Since the 1.4 update, if you log out on a ladder, upon relogging you will be teleported to the top of the ladder.

Lightning

 * Lightning can strike inside houses and caves.
 * If lightning strikes inside a wooden house it is lost forever.
 * If lightning strikes inside a cave you will burn to death.

Minecarts

 * Engines consume coal but do not move under their own power, making them useless.
 * Empty/Storage Minecarts start to behave strangely when they are too far away from the Player. They disappear completely, disappear until Players disconnect and reconnect, or suddenly stop on tracks despite having sufficient momentum.
 * Minecarts load before terrain sometimes causing them to be invisible until they are interacted with. Large transit systems and door water boosters are examples of when the issue occurs. (log out/in to reproduce).

Mobs, Hostile

 * Shooting animations (Ghast fireballs/opening mouth and eyes, Skeleton arrows) are not always visible. The sound of these actions (Ghast scream and Skeleton "twang") cannot be heard either.
 * Ghasts' fireballs occasionally do not explode, only lighting a small area on fire.
 * Sometimes mobs freeze in animation and can not be hit. They disappear after about 2 minutes. They are client-sided, so no other players will see them.
 * Some users are reporting mobs will be invisible, but can still attack you. On update 11/24/2010 SMP health update post Notch explained that to see invisible mobs, players must set their difficulty to the server side difficulty or higher.
 * This does not always fix the problem; on occasion, mobs will fail to load client-side.
 * Sometimes when the character dies, monsters will stay loaded client-side and not be loaded on the server side.
 * Sometimes players can hit mobs multiple times before the server registers the hit. The hits will then all register at once and the mob will be subjected to several knockbacks at once, flying into the air.
 * When a mob dies, its corpse sometimes sticks in the red death animation and doesn't despawn.
 * When slimes divide in SMP they may create client-side duplicates.
 * The lower half of mobs can not be hit with a melee weapon when you are 1-2 blocks below them. They can, however, be hit from directly underneath.

Mobs, Passive

 * Squids can fly upwards.
 * Placed "pig" monster spawners create client-side pigs.

Paintings

 * When copying an SSP world onto an SMP server, paintings are removed in the transition.
 * Paintings can be destroyed in spawn-protected areas

Sand and Snow

 * Sand will not fall down if a non-solid block underneath it.

Redstone

 * Since Beta 1.4, pulsars do not work, and many circuits have become glitchy in SMP.
 * The particle colors for Delay/repeater blocks are the same of pumpkins.

TNT

 * TNT lit by one user cannot be seen by another, though its effects can.
 * Occasionally, a TNT block meant to drop will enter a repeating fall animation (but not actually fall) when lit. When the TNT finally explodes, it will explode at the position it was placed.
 * Occasionally, a TNT block can also explode twice, but this will not damage the environment twice.
 * If a lot of TNT is lit, some TNT may explode but leave behind an image of an exploding TNT block that is almost completely white, and will hover in mid-air while repeating the falling animation. The ghost TNT will not disappear unless the player disconnects and reconnects. (This is a client-side TNT entity)

Trees

 * Trees that have grown recently, especially packed together in a tree farm, sometimes don't update the client with the leaf positions. This creates "invisible" leaves that the player can't walk through and makes navigating tree farms an annoyance.
 * Using bone meal to quick-grow trees will sometimes cause "floating" trees to grow with the sapling still at the base. Removing the sapling or using more bone meal can cause the tree to grow into an enormous bundle of leaves with no log base. These leaves will now respawn immediately after being harvested. The only way to remove these glitched leaf blocks is to burn each block individually (fire will not spread for some reason) OR set the floor below the leaves on fire OR build an umbrella above it, the shadow seems to instantly vanquish the leaves. - This glitch is vastly more common when quick-growing trees under another trees foliage. Again, disconnecting and reconnecting will reset these "ghost trees."
 * Planting a sapling and waiting a bit will sometimes yield tree trunks with weird distributions of leaves, and in some cases, no leaves at all. Trees can also grow but be invisible, making it impossible to traverse a tree farm after a while. Rejoining the server appears to make invisible trees visible again and fire will swiftly cause phantom foliage to be made manifest. You can also place a torch to make the phantom foliage appear.
 * Leaves from trees will overwrite some blocks, such as a nearby fence.
 * Placing a torch on Leaves does not make the 'pop' sound for the item being placed.
 * When a tree's detached from the ground (floating), the wood blocks should degrade; similar to how leaves disappear if detached from wood.

Water

 * You may find yourself drowning despite having a full breath meter. This is caused by the client registering that the player has gotten air, but the server registers that the player is still underwater. This causes the non-synced breath meter.