webchimp

Having a similar problem, worked fine a couple of days ago.
Tried deleting everything in '.minecraft' and re-installing the launcher
Tried different versions.
Found this in the game output screen trying to play a vanilla 1.8.3 game

AL lib: (EE) DoReset: Failed to initialize audio client: 0x8007000e
Exception in thread "Thread-6" org.lwjgl.openal.OpenALException: Invalid Device
at org.lwjgl.openal.Util.checkALCError(Util.java:55)
at org.lwjgl.openal.ALC10.alcCreateContext(ALC10.java:251)
at org.lwjgl.openal.AL.init(AL.java:173)
at org.lwjgl.openal.AL.create(AL.java:143)
at org.lwjgl.openal.AL.create(AL.java:102)
at org.lwjgl.openal.AL.create(AL.java:206)
at paulscode.sound.libraries.LibraryLWJGLOpenAL.init(LibraryLWJGLOpenAL.java:164)
at paulscode.sound.SoundSystem.CommandNewLibrary(SoundSystem.java:1576)
at paulscode.sound.SoundSystem.CommandQueue(SoundSystem.java:2572)
at paulscode.sound.CommandThread.run(CommandThread.java:121)

also found this in the log

[16:42:26 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_31]
at java.util.ArrayList$Itr.next(Unknown Source) ~[?:1.8.0_31]
at net.minecraft.launcher.updater.MinecraftVersionManager.getInstalledVersions(MinecraftVersionManager.java:185) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.Launcher.cleanupOrphanedVersions(Launcher.java:430) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.Launcher.performCleanups(Launcher.java:494) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.game.MinecraftGameRunner.launchGame(MinecraftGameRunner.java:221) ~[launcher.jar:1.6.11]
at com.mojang.launcher.game.runner.AbstractGameRunner.onDownloadJobFinished(AbstractGameRunner.java:186) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:122) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:86) [launcher.jar:1.6.11]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_31]
at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_31]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.8.0_31]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.8.0_31]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_31]

I'm getting this in 1.7.10, which is annoying because there's a jungle next to my base and my mine goes under it.

Gets really laggy.

Phenom II x6 3.3, 750ti, 4GB ram dedicated to MC, game runs off an SSD.

I do have treecapacitor though, so I'm sure if I do nothing else for a couple of days I can probably cure the problem.

Preben- Just noticed that when I got back to my base.

The baby cows no longer die when they enter a one high space, unless there is flowing water, such as in a transport tunnel in a cow farm. If you go back to 1.6.2 baby cows do not suffocate in a 1 high tunnel with flowing water.

I've been having a bit of an experiment with this (14w11b), like other people I've had Friendly Creatures turned down because of animal farms and didn't realise until now that that was what was causing the no-footstep sounds.

Turned everything else down and Friendly Creatures up and tested walking on stuff.

Dirt, gravel & wood I can hear fine.
Snow is very quiet.
Grass and stone are virtual too quiet to hear unless I crank the volume on the stereo up and that makes the other sounds too loud.

Maybe this sort of stuff could be placed under Player sounds.

Also I've just realised that turning Blocks down makes doors and chests far less annoying,.

Floating torch

I'm having a similar issue, my cow breeding facility had a 1 high space with a water flow in it to bring the baby cows to the point they get dropped out into a pasture area to grow up. At least half the cows were dying on the way out.

I changed this to a two high gap with a water flow and they still die (albeit slower) as they bounce up and down and hit their heads on the blocks above.

I remade it with a three high gap and a water flow and they all survive now.

Might be something to do with the new hit boxes. Not that then.