Hey guys, I have a big problem when playing on my friends dedicated server. Whenever I try and do anything related to inventory whether that be pressing I, opening furnaces or chests etc my minecraft crashs completly. It works on single player and this is happening on two different pc's. Anyone else had this problem or know what might be causing it or how to fix it?
this is the error
      Minecraft has crashed!     
      ----------------------     

Minecraft has stopped running because it encountered a problem.

If you wish to report this, please copy this entire text and email it to

.
Please include a description of what you did when the error occured.

--- BEGIN ERROR REPORT a1dce528 --------
Generated 17/12/10 20:23

Minecraft: Minecraft Alpha v1.2.6
OS: Windows Vista (x86) version 6.0
Java: 1.6.0_17, Sun Microsystems Inc.
VM: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
LWJGL: 2.4.2
OpenGL: GeForce 8600 GT/PCI/SSE2/3DNOW! version 3.3.0, NVIDIA Corporation

java.lang.NullPointerException
    at fp.b(SourceFile:67)
    at af.a(SourceFile:131)
    at ex.a(SourceFile:113)
    at ex.a(SourceFile:46)
    at ne.a(SourceFile:68)
    at kb.b(SourceFile:331)
    at net.minecraft.client.Minecraft.run(SourceFile:622)
    at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT c44532b7 ----------