Hopper: java.lang.ArrayIndexOutOfBoundsException: -1

java.lang.ArrayIndexOutOfBoundsException: -1
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.b(SourceFile:68)
	at acv.a(SourceFile:61)
	at adr.a(SourceFile:865)
	at abw.a(SourceFile:92)
	at abw.d(SourceFile:1925)
	at abw.y(SourceFile:1921)
	at js.g(SourceFile:257)
	at js.b(SourceFile:133)

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 9/19/13 10:45 PM
Description: Exception ticking world

java.lang.ArrayIndexOutOfBoundsException: -1
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.b(SourceFile:68)
	at acv.a(SourceFile:61)
	at adr.a(SourceFile:865)
	at abw.a(SourceFile:92)
	at abw.d(SourceFile:1925)
	at abw.y(SourceFile:1921)
	at js.g(SourceFile:257)
	at js.b(SourceFile:133)
	at net.minecraft.server.MinecraftServer.t(SourceFile:463)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)


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

-- Head --
Stacktrace:
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.b(SourceFile:68)
	at acv.a(SourceFile:61)
	at adr.a(SourceFile:865)
	at abw.a(SourceFile:92)
	at abw.d(SourceFile:1925)
	at abw.y(SourceFile:1921)
	at js.g(SourceFile:257)
	at js.b(SourceFile:133)

-- Affected level --
Details:
	Level name: Untitled World
	All players: 1 total; [jv['MIGHTPREADATOR'/55458, l='Untitled World', x=-1.57, y=64.00, z=15.72]]
	Chunk stats: ServerChunkCache: 625 Drop: 0
	Level seed: -6815097636558329856
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (0,65,0), Chunk: (at 0,4,0 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: 3724 game time, 3724 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 90678 (now: false), thunder time: 44277 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:463)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 321185248 bytes (306 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 1675 (93800 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 22, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 103 (5768 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Player Count: 1 / 8; [jv['MIGHTPREADATOR'/55458, l='Untitled World', x=-1.57, y=64.00, z=15.72]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.