java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at agm.a(SourceFile:176)
	at agm.a(SourceFile:27)
	at agg.a(SourceFile:362)
	at ago.a(SourceFile:29)
	at apg.a(SourceFile:162)
	at mi.a(SourceFile:160)
	at aoj.a(SourceFile:781)
	at mi.c(SourceFile:95)
	at mi.d(SourceFile:108)
	at afn.e(SourceFile:311)

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 26/10/13 17.28
Description: Exception getting block type in world

java.lang.IllegalArgumentException: n must be positive
	at java.util.Random.nextInt(Unknown Source)
	at agm.a(SourceFile:176)
	at agm.a(SourceFile:27)
	at agg.a(SourceFile:362)
	at ago.a(SourceFile:29)
	at apg.a(SourceFile:162)
	at mi.a(SourceFile:160)
	at aoj.a(SourceFile:781)
	at mi.c(SourceFile:95)
	at mi.d(SourceFile:108)
	at afn.e(SourceFile:311)
	at afn.a(SourceFile:249)
	at afn.e(SourceFile:477)
	at afn.d(SourceFile:463)
	at afn.c(SourceFile:428)
	at afn.d(SourceFile:337)
	at afn.f(SourceFile:390)
	at ajj.m(SourceFile:46)
	at ajj.a(SourceFile:35)
	at mj.a(SourceFile:405)
	at mj.b(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:503)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)


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

-- Head --
Stacktrace:
	at java.util.Random.nextInt(Unknown Source)
	at agm.a(SourceFile:176)
	at agm.a(SourceFile:27)
	at agg.a(SourceFile:362)
	at ago.a(SourceFile:29)
	at apg.a(SourceFile:162)
	at mi.a(SourceFile:160)
	at aoj.a(SourceFile:781)
	at mi.c(SourceFile:95)
	at mi.d(SourceFile:108)
	at afn.e(SourceFile:311)

-- Requested block coordinates --
Details:
	Found chunk: true
	Location: World: (-1056,4,240), Chunk: (at 0,0,0 in -66,15; contains blocks -1056,0,240 to -1041,255,255), Region: (-3,0; contains chunks -96,0 to -65,31, blocks -1536,0,0 to -1025,255,511)
Stacktrace:
	at afn.a(SourceFile:249)
	at afn.e(SourceFile:477)
	at afn.d(SourceFile:463)
	at afn.c(SourceFile:428)
	at afn.d(SourceFile:337)
	at afn.f(SourceFile:390)
	at ajj.m(SourceFile:46)
	at ajj.a(SourceFile:35)

-- Block being ticked --
Details:
	Block type: ID #12 (tile.sand // alt)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-1056,4,239), Chunk: (at 0,0,15 in -66,14; contains blocks -1056,0,224 to -1041,255,239), Region: (-3,0; contains chunks -96,0 to -65,31, blocks -1536,0,0 to -1025,255,511)
Stacktrace:
	at mj.a(SourceFile:405)
	at mj.b(SourceFile:134)

-- Affected level --
Details:
	Level name: Nuovo Mondo
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 472 Drop: 0
	Level seed: -1279782693552188917
	Level generator: ID 01 - flat, ver 0. Features enabled: true
	Level generator options: 2;8x12;2;stronghold,biome_1,village,decoration,dungeon,mineshaft
	Level spawn location: World: (-1016,4,103), Chunk: (at 8,0,7 in -64,6; contains blocks -1024,0,96 to -1009,255,111), Region: (-2,0; contains chunks -64,0 to -33,31, blocks -1024,0,0 to -513,255,511)
	Level time: 703 game time, 703 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 48932 (now: false), thunder time: 131495 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.u(SourceFile:503)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsk.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at ky.run(SourceFile:617)

-- System Details --
Details:
	Minecraft Version: 1.7.2
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_11, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 51424144 bytes (49 MB) / 503906304 bytes (480 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 343821 (19253976 bytes; 18 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 131 (7336 bytes; 0 MB) allocated, 0 (0 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.