I have Ubuntu 11.10 64-bit and I installed JDK 1.7.0 update 2 x64 via webupd8 page. But currently I have problem with minecraft game. After downloading launcher from Minecraft.net and lauch the game by java -jar /home/zrebec/Downloads/minecraft.jar launcehr is launched normaly, after login the game download the updates but then I got just the black screen with this in terminal:

Setting user: zrebec, -356009615199623309
Exception in thread "Minecraft main thread" java.lang.UnsatisfiedLinkError: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: wrong ELF class: ELFCLASS32 (Possible cause: architecture word width mismatch)
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1928)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1825)
at java.lang.Runtime.load0(Runtime.java:792)
at java.lang.System.load(System.java:1059)
at org.lwjgl.Sys$1.run(Sys.java:69)
at java.security.AccessController.doPrivileged(Native Method)
at org.lwjgl.Sys.doLoadLibrary(Sys.java:65)
at org.lwjgl.Sys.loadLibrary(Sys.java:81)
at org.lwjgl.Sys.<clinit>(Sys.java:98)
at org.lwjgl.opengl.Display.<clinit>(Display.java:132)
at net.minecraft.client.Minecraft.a(SourceFile:180)
at net.minecraft.client.Minecraft.run(SourceFile:648)
at java.lang.Thread.run(Thread.java:722)

Please anyone can help me with this? I think that problem will be in architecture becase:

liblwjgl.so: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: wrong ELF class: ELFCLASS32 (Possible cause: architecture word width mismatch)

Any idea please?

I know, maybe this one is off topic because maybe its not Ubuntu problem maybe but in 64-bit works all perfectly and I think that accepted answer can help to many users and can make better playing games under linux. Really. Thank you very much for any idea.