Minecraft has crashed!
----------------------

Minecraft has stopped running because it encountered a problem; Exception while ticking a block

A full error report has been saved to C:\Users\Matt\AppData\Roaming\.minecraft\crash-reports\crash-2012-12-25_09.27.17-server.txt - Please include a copy of that file (Not this screen!) if you report this crash to anyone; without it, they will not be able to help fix the crash

— BEGIN ERROR REPORT b475ab92 --------
Full report at:
C:\Users\Matt\AppData\Roaming\.minecraft\crash-reports\crash-2012-12-25_09.27.17-server.txt
Please show that file to Mojang, NOT just this screen!

Generated 12/25/12 9:27 AM

– Head –
Stacktrace:
at ii.a(SourceFile:69)
at ii.a(SourceFile:56)
at ij.a(SourceFile:24)
at yc.a(SourceFile:842)
at in.a(SourceFile:580)
at yc.d(SourceFile:834)
at akn.l(SourceFile:55)
at akn.b(SourceFile:35)

– Block being ticked –
Details:
Block type: ID #12 (tile.sand // akn)
Block data value: 0 / 0x0 / 0b0000
Block location: World: (139,48,127), Chunk: (at 11,3,15 in 8,7; contains blocks 128,0,112 to 143,255,127), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Stacktrace:
at in.a(SourceFile:388)
at in.b(SourceFile:136)

– Affected level –
Details:
Level name: Matthews_World
All players: 1 total; [iq['SmoothMatthew'/71, l='Matthews_World', x=221.50, y=55.00, z=98.50]]
Chunk stats: ServerChunkCache: 625 Drop: 0
Level seed: -4393473688695275855
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (228,64,100), Chunk: (at 4,4,4 in 14,6; contains blocks 224,0,96 to 239,255,111), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 330 game time, 330 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 38391 (now: false), thunder time: 142314 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.r(SourceFile:736)
at net.minecraft.server.MinecraftServer.q(SourceFile:679)
at bdz.q(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:613)
at fy.run(SourceFile:849)

– System Details –
Details:
Minecraft Version: 1.4.6
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.6.0_14, Sun Microsystems Inc.
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
Memory: 387172560 bytes (369 MB) / 532807680 bytes (508 MB) up to 1065484288 bytes (1016 MB)
JVM Flags: 2 total; -Xms512m -Xmx1024m
AABB Pool Size: 9228 (516768 bytes; 0 MB) allocated, 0 (0 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: 4693 (262808 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [iq['SmoothMatthew'/71, l='Matthews_World', x=221.50, y=55.00, z=98.50]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

java.lang.IllegalStateException: Entity is already tracked!
at ii.a(SourceFile:69)
at ii.a(SourceFile:56)
at ij.a(SourceFile:24)
at yc.a(SourceFile:842)
at in.a(SourceFile:580)
at yc.d(SourceFile:834)
at akn.l(SourceFile:55)
at akn.b(SourceFile:35)
at in.a(SourceFile:388)
at in.b(SourceFile:136)
at net.minecraft.server.MinecraftServer.r(SourceFile:736)
at net.minecraft.server.MinecraftServer.q(SourceFile:679)
at bdz.q(SourceFile:117)
at net.minecraft.server.MinecraftServer.run(SourceFile:613)
at fy.run(SourceFile:849)
— END ERROR REPORT 7d92bde ----------