Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at bcw.a(SourceFile:902)
	at gf.a(SourceFile:44)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bcy.c(SourceFile:71)

---- Minecraft Crash Report ----
// Everything's going to plan. No, really, that was supposed to happen.

Time: 01.10.13 20:36
Description: Ticking screen

java.lang.NullPointerException
	at bcw.a(SourceFile:902)
	at gf.a(SourceFile:44)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bcy.c(SourceFile:71)
	at atv.k(SourceFile:1173)
	at atv.S(SourceFile:663)
	at atv.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at bcw.a(SourceFile:902)
	at gf.a(SourceFile:44)
	at co.b(SourceFile:354)
	at bcw.e(SourceFile:98)
	at bcy.c(SourceFile:71)

-- Affected screen --
Details:
	Screen name: bcy
Stacktrace:
	at atv.k(SourceFile:1173)
	at atv.S(SourceFile:663)
	at atv.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 39550928 bytes (37 MB) / 69558272 bytes (66 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.6.4
	LWJGL: 2.9.0
	OpenGL: GeForce 8800 GTX/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: Deutsch (Deutschland)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null