block 34:6 crashes game

---- Minecraft Crash Report ----
// Why did you do that?

Time: 2-12-12 19:02
Description: Exception while updating neighbours

java.lang.ArrayIndexOutOfBoundsException: 6
	at ant.a(SourceFile:184)
	at xv.m(SourceFile:442)
	at xv.h(SourceFile:430)
	at xv.f(SourceFile:384)
	at xv.d(SourceFile:371)
	at pw.j_(SourceFile:106)
	at xv.a(SourceFile:1317)
	at in.a(SourceFile:451)
	at xv.g(SourceFile:1296)
	at xv.h(SourceFile:1195)
	at in.h(SourceFile:363)
	at net.minecraft.server.MinecraftServer.r(SourceFile:751)
	at net.minecraft.server.MinecraftServer.q(SourceFile:686)
	at bdo.q(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:620)
	at fy.run(SourceFile:856)


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

-- Head --
Stacktrace:
	at ant.a(SourceFile:184)

-- Block being updated --
Details:
	Source block type: ID #1 (tile.stone // ame)
	Block type: ID #34 (null // ant)
	Block data value: 6 / 0x6 / 0b0110
	Block location: World: (-267,69,257), Chunk: (at 5,4,1 in -17,16; contains blocks -272,0,256 to -257,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Stacktrace:
	at xv.m(SourceFile:442)
	at xv.h(SourceFile:430)
	at xv.f(SourceFile:384)
	at xv.d(SourceFile:371)
	at pw.j_(SourceFile:106)
	at xv.a(SourceFile:1317)
	at in.a(SourceFile:451)
	at xv.g(SourceFile:1296)

-- Entity being ticked --
Details:
	Entity Type: FallingSand (pw)
	Entity ID: 5
	Name: Falling Block
	Exact location: -266,50, 68,00, 257,50
	Block location: World: (-267,68,257), Chunk: (at 5,4,1 in -17,16; contains blocks -272,0,256 to -257,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Momentum: 0,00, -0,00, 0,00
Stacktrace:
	at xv.h(SourceFile:1195)
	at in.h(SourceFile:363)

-- Affected level --
Details:
	Level name: new test world
	All players: 0 total; []
	Chunk stats: ServerChunkCache: 628 Drop: 0
	Level seed: -7347323372672619410
	Level generator: ID 01 - flat, ver 0. Features enabled: true
	Level generator options: 1;7,59x1,3x3,2;1
	Level spawn location: World: (-179,72,211), Chunk: (at 13,4,3 in -12,13; contains blocks -192,0,208 to -177,255,223), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
	Level time: 1431444 game time, 7502 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 55261 (now: false), thunder time: 48330 (now: true)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.r(SourceFile:751)
	at net.minecraft.server.MinecraftServer.q(SourceFile:686)
	at bdo.q(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:620)
	at fy.run(SourceFile:856)

-- System Details --
Details:
	Minecraft Version: 1.4.5
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_09, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 357115544 bytes (340 MB) / 514523136 bytes (490 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	AABB Pool Size: 55 (3080 bytes; 0 MB) allocated, 55 (3080 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 4 (224 bytes; 0 MB) allocated, 4 (224 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.