Hopper: java.util.ConcurrentModificationException (SourceFile:52)

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-500/

Crash:

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap.putAllForCreate(Unknown Source)
	at java.util.HashMap.<init>(Unknown Source)
	at bls.b(SourceFile:52)
	at bls.e(SourceFile:209)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 02.08.13 14:22
Description: Unexpected error

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap.putAllForCreate(Unknown Source)
	at java.util.HashMap.<init>(Unknown Source)
	at bls.b(SourceFile:52)
	at bls.e(SourceFile:209)
	at ats.k(SourceFile:1129)
	at ats.S(SourceFile:663)
	at ats.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 java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap$EntryIterator.next(Unknown Source)
	at java.util.HashMap.putAllForCreate(Unknown Source)
	at java.util.HashMap.<init>(Unknown Source)
	at bls.b(SourceFile:52)
	at bls.e(SourceFile:209)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdf['Player'/69, l='MpServer', x=254,30, y=55,62, z=-80,37]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (216,64,-92), Chunk: (at 8,4,4 in 13,-6; contains blocks 208,0,-96 to 223,255,-81), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Level time: 32740 game time, 32740 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: survival (ID 0). Hardcore: false. Cheats: false
	Forced entities: 33 total; [rn['Bat'/258267, l='MpServer', x=288,53, y=19,73, z=-93,84], rx['Pig'/17, l='MpServer', x=190,50, y=70,00, z=-147,22], rx['Pig'/16, l='MpServer', x=192,03, y=69,00, z=-150,56], rx['Pig'/19, l='MpServer', x=189,03, y=70,00, z=-149,91], rx['Pig'/18, l='MpServer', x=196,22, y=74,00, z=-149,81], ry['Sheep'/34, l='MpServer', x=251,47, y=70,00, z=-133,28], ry['Sheep'/32, l='MpServer', x=266,91, y=68,00, z=-131,16], ry['Sheep'/33, l='MpServer', x=236,94, y=64,00, z=-125,97], ry['Sheep'/51, l='MpServer', x=299,50, y=76,00, z=-125,50], ry['Sheep'/50, l='MpServer', x=297,50, y=70,00, z=-123,50], ry['Sheep'/49, l='MpServer', x=297,31, y=70,00, z=-125,09], ry['Sheep'/48, l='MpServer', x=288,09, y=71,00, z=-136,19], ry['Sheep'/59, l='MpServer', x=329,50, y=70,00, z=-131,94], ry['Sheep'/58, l='MpServer', x=331,50, y=69,00, z=-132,50], ry['Sheep'/61, l='MpServer', x=328,50, y=68,00, z=-128,50], ry['Sheep'/60, l='MpServer', x=328,50, y=70,00, z=-130,50], bdf['Player'/69, l='MpServer', x=254,30, y=55,62, z=-80,37], rn['Bat'/262647, l='MpServer', x=201,75, y=29,00, z=-66,56], rn['Bat'/256218, l='MpServer', x=282,50, y=28,70, z=-81,41], sb['Squid'/113438, l='MpServer', x=257,32, y=46,13, z=-63,53], rn['Bat'/248052, l='MpServer', x=234,56, y=25,48, z=-22,91], sb['Squid'/236188, l='MpServer', x=222,13, y=52,34, z=-26,66], rn['Bat'/259155, l='MpServer', x=312,97, y=27,82, z=-3,00], rn['Bat'/259157, l='MpServer', x=284,25, y=19,42, z=-10,72], rn['Bat'/259156, l='MpServer', x=304,50, y=24,10, z=-20,25], rn['Bat'/259161, l='MpServer', x=301,25, y=28,21, z=-6,63], sb['Squid'/18710, l='MpServer', x=256,20, y=46,38, z=-64,50], sb['Squid'/22554, l='MpServer', x=252,50, y=46,00, z=-63,89], rn['Bat'/263988, l='MpServer', x=303,78, y=16,82, z=-158,44], rn['Bat'/263983, l='MpServer', x=302,69, y=18,54, z=-158,72], sr['item.item.sulphur'/248843, l='MpServer', x=231,84, y=30,13, z=-61,81], sb['Squid'/198932, l='MpServer', x=259,34, y=47,51, z=-66,23], sb['Squid'/198933, l='MpServer', x=252,86, y=46,18, z=-63,50]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bda.a(SourceFile:284)
	at ats.b(SourceFile:1761)
	at ats.d(SourceFile:633)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.6.0_13, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Sun Microsystems Inc.
	Memory: 57539664 bytes (54 MB) / 227647488 bytes (217 MB) up to 532742144 bytes (508 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 22182 (1242192 bytes; 1 MB) allocated, 1684 (94304 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.2
	LWJGL: 2.9.0
	OpenGL: GeForce4 MX 440 with AGP8X/AGP/SSE/3DNOW! GL version 1.5.3, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 31141 (1743896 bytes; 1 MB) allocated, 417 (23352 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-500/5481/