After I tried OpenJDK 7 on Ubuntu 64 Bit I got the error about a wrong ELFCLASS32 (OpenJDK 6 is working fine). This happened on the distributed version of LWJGL in Minecraft (a version before 2.7.1 but I can't say exactly which) and on version 2.7.1. So I tried a build of version 2.8.0 (#1349) but the sound doesn't load anymore. I get this output:
QuoteStarting up SoundSystem...
Initializing LWJGL OpenAL
(The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Exception in thread "Thread-9" java.lang.UnsatisfiedLinkError: org.lwjgl.openal.AL10.initNativeStubs()V
at org.lwjgl.openal.AL10.initNativeStubs(Native Method)
at org.lwjgl.openal.AL.init(AL.java:156)
at org.lwjgl.openal.AL.create(AL.java:138)
at org.lwjgl.openal.AL.create(AL.java:102)
at org.lwjgl.openal.AL.create(AL.java:201)
at paulscode.sound.libraries.LibraryLWJGLOpenAL.init(SourceFile:162)
at paulscode.sound.SoundSystem.CommandNewLibrary(SourceFile:1489)
at paulscode.sound.SoundSystem.CommandQueue(SourceFile:2362)
at paulscode.sound.CommandThread.run(SourceFile:121)
ERROR MESSAGE:
SoundSystem did not load after 30 seconds.
Starting up SoundSystem...
Switching to No Sound
(Silent Mode)
But I don't know if this is an incompatibility of Minecraft with LWJGL 2.8.0 or a bug in LWJGL 2.8.0.
this is a known bug with the current LWJGL nightly builds, see this thread (http://lwjgl.org/forum/index.php/topic,4174.0.html).