Hey can anybody tell me why my minecraft is not working, your help would be much appreaciated

--- BEGIN ERROR REPORT a1dce528 --------
Generated 06/02/11 16:50

Minecraft: Minecraft Beta 1.2_02
OS: Windows 7 (x86) version 6.1
Java: 1.6.0_23, Sun Microsystems Inc.
VM: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
LWJGL: 2.4.2
OpenGL: ATI Radeon HD 5570 version 3.2.9405 Compatibility Profile Context, ATI Technologies Inc.

java.nio.BufferOverflowException
 at java.nio.DirectByteBuffer.put(Unknown Source)
 at java.nio.ByteBuffer.put(Unknown Source)
 at gs.a(SourceFile:148)
 at gs.a(SourceFile:62)
 at net.minecraft.client.Minecraft.i(SourceFile:1086)
 at net.minecraft.client.Minecraft.run(SourceFile:642)
 at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT df54f8cd ----------