My game will close when I try to go into a server repeatedly.

---- Minecraft Crash Report ----
// I let you down. Sorry :(

Time: 7/5/13 1:00 AM
Description: Unexpected error

java.lang.NullPointerException
	at bey.a(SourceFile:509)
	at bey.b(SourceFile:467)
	at bet.b(SourceFile:474)
	at bet.a(SourceFile:930)
	at bet.b(SourceFile:695)
	at atn.S(SourceFile:685)
	at atn.d(SourceFile:618)
	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 bey.a(SourceFile:509)
	at bey.b(SourceFile:467)
	at bet.b(SourceFile:474)
	at bet.a(SourceFile:930)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bcx['SimonCowan'/2670677, l='MpServer', x=-11955.74, y=57.82, z=5119.55]]
	Chunk stats: MultiplayerChunkCache: 49
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-3760,66,9396), Chunk: (at 0,4,4 in -235,587; contains blocks -3760,0,9392 to -3745,255,9407), Region: (-8,18; contains chunks -256,576 to -225,607, blocks -4096,0,9216 to -3585,255,9727)
	Level time: 322910355 game time, 37217166001 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 16 total; [oi['Painting'/2670678, l='MpServer', x=-11964.50, y=55.00, z=5118.94], bcx['SimonCowan'/2670677, l='MpServer', x=-11955.74, y=57.82, z=5119.55], oa['entity.ItemFrame.name'/2670679, l='MpServer', x=-11965.50, y=54.50, z=5114.06], oi['Painting'/2670678, l='MpServer', x=-11964.50, y=55.00, z=5118.94], oi['Painting'/2670681, l='MpServer', x=-11965.94, y=69.00, z=5099.00], oi['Painting'/2670682, l='MpServer', x=-11965.94, y=69.00, z=5089.00], oi['Painting'/2670683, l='MpServer', x=-11958.50, y=77.00, z=5102.94], oi['Painting'/2670684, l='MpServer', x=-11981.00, y=69.00, z=5116.94], oi['Painting'/2670685, l='MpServer', x=-11981.00, y=74.00, z=5116.94], oa['entity.ItemFrame.name'/2670687, l='MpServer', x=-11985.94, y=59.50, z=5091.50], oi['Painting'/2670684, l='MpServer', x=-11981.00, y=69.00, z=5116.94], oi['Painting'/2670685, l='MpServer', x=-11981.00, y=74.00, z=5116.94], oi['Painting'/2670682, l='MpServer', x=-11965.94, y=69.00, z=5089.00], oi['Painting'/2670683, l='MpServer', x=-11958.50, y=77.00, z=5102.94], oa['entity.ItemFrame.name'/2670680, l='MpServer', x=-11964.50, y=54.50, z=5114.06], oi['Painting'/2670681, l='MpServer', x=-11965.94, y=69.00, z=5099.00]]
	Retry entities: 0 total; []
Stacktrace:
	at bcu.a(SourceFile:284)
	at atn.b(SourceFile:1743)
	at atn.d(SourceFile:632)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows 8 (amd64) version 6.2
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 137921320 bytes (131 MB) / 351404032 bytes (335 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 18931 (1060136 bytes; 1 MB) allocated, 10996 (615776 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.1
	LWJGL: 2.9.0
	OpenGL: AMD Radeon HD 6520G GL version 4.2.11931 Compatibility Profile Context, ATI Technologies Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 43 (2408 bytes; 0 MB) allocated, 43 (2408 bytes; 0 MB) used