---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 2013-03-15 15:23
Description: Exception ticking world

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at aah.a(SourceFile:72)
	at iz.b(SourceFile:119)
	at net.minecraft.server.MinecraftServer.r(SourceFile:454)
	at net.minecraft.server.MinecraftServer.q(SourceFile:397)
	at bja.q(SourceFile:122)
	at net.minecraft.server.MinecraftServer.run(SourceFile:331)
	at gp.run(SourceFile:573)


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

-- Head --
Stacktrace:
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at aah.a(SourceFile:72)
	at iz.b(SourceFile:119)

-- Affected level --
Details:
	Level name: ssp
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 0 Drop: 0
	Level seed: 1403159560
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 0 game time, 0 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: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at net.minecraft.server.MinecraftServer.r(SourceFile:454)
	at net.minecraft.server.MinecraftServer.q(SourceFile:397)
	at bja.q(SourceFile:122)
	at net.minecraft.server.MinecraftServer.run(SourceFile:331)
	at gp.run(SourceFile:573)

-- System Details --
Details:
	Minecraft Version: 1.5
	Operating System: Windows Vista (x86) version 6.0
	Java Version: 1.6.0_31, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
	Memory: 527492072 bytes (503 MB) / 865099776 bytes (825 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	AABB Pool Size: 235463 (13185928 bytes; 12 MB) allocated, 310 (17360 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 20841 (1167096 bytes; 1 MB) allocated, 90 (5040 bytes; 0 MB) used
	Player Count: 0 / 8; []
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.