Computer craft 1.63 [the bug may work with V. 1.6 / 1.61 / 1.62, too]
Forge: 9.11.1.965

Crash log:

SpoilerTime: 24/04/14 19:06
Description: Exception ticking world

java.lang.NullPointerException
at net.minecraft.world.WorldServer.func_73043_a(WorldServer.java:1074)
at net.minecraft.world.WorldServer.func_73055_Q(WorldServer.java:1058)
at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:212)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:657)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)


A detailed walkthrough of the error, its code path and all known details is as follows:
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– Head –
Stacktrace:
at net.minecraft.world.WorldServer.func_73043_a(WorldServer.java:1074)
at net.minecraft.world.WorldServer.func_73055_Q(WorldServer.java:1058)
at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:212)

– Affected level –
Details:
Level name: New World
All players: 1 total; [EntityPlayerMP['Mathsjc'/10, l='New World', x=1471,42, y=4,00, z=1489,07]]
Chunk stats: ServerChunkCache: 1369 Drop: 0
Level seed: 7122779305014530807
Level generator: ID 01 - flat, ver 0. Features enabled: true
Level generator options:
Level spawn location: World: (1476,4,1495), Chunk: (at 4,0,7 in 92,93; contains blocks 1472,0,1488 to 1487,255,1503), Region: (2,2; contains chunks 64,64 to 95,95, blocks 1024,0,1024 to 1535,255,1535)
Level time: 2309 game time, 2309 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 117849 (now: false), thunder time: 149021 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:657)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

– System Details –
Details:
Minecraft Version: 1.6.4
Operating System: Linux (amd64) version 3.13.10-200.fc20.x86_64
Java Version: 1.7.0_55, Oracle Corporation
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 240600160 bytes (229 MB) / 590872576 bytes (563 MB) up to 954728448 bytes (910 MB)
JVM Flags: 1 total; -Xmx1G
AABB Pool Size: 522 (29232 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Suspicious classes: FML and Forge are installed
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v8.11 FML v6.4.49.965 Minecraft Forge 9.11.1.965 4 mods loaded, 4 mods active
mcp{8.09} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{6.4.49.965} [Forge Mod Loader] (minecraftforge-9.11.1.965.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{9.11.1.965} [Minecraft Forge] (minecraftforge-9.11.1.965.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ComputerCraft{1.63} [ComputerCraft] (Computer Craft 1.63.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 58 (3248 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['Mathsjc'/10, l='New World', x=1471,42, y=4,00, z=1489,07]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'

How to reproduce it:

Place a Disk Drive
Insert any minecraft music disk in the Disk Drive
Place a computer on a side of Disk Drive
Do dj in the computer
Break the disk drive while the disk is playing
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Sorry about any grammar mistake (I'm not a native speaker) and if this post is a duplicate

edit: crash the SMP host server, too