Simple Crash

Was building a Gravel path. Upon breaking a piece of Gravel the game crashed. Not sure why.

---- Minecraft Crash Report ----
// I just don't know what went wrong :(

Time: 12/21/12 10:58 PM
Description: Ticking memory connection

java.lang.IllegalStateException: Entity is already tracked!
	at ii.a(SourceFile:69)
	at ii.a(SourceFile:53)
	at ij.a(SourceFile:24)
	at yc.a(SourceFile:842)
	at in.a(SourceFile:580)
	at yc.a(SourceFile:2150)
	at zz.c(SourceFile:594)
	at im.c(SourceFile:101)
	at il.<init>(SourceFile:26)
	at ik.a(SourceFile:172)
	at ik.d(SourceFile:300)
	at gm.d(SourceFile:156)
	at iv.a(SourceFile:275)
	at eb.a(SourceFile:136)
	at cf.b(SourceFile:55)
	at iv.d(SourceFile:57)
	at iw.b(SourceFile:39)
	at bec.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.r(SourceFile:762)
	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)


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

-- System Details --
Details:
	Minecraft Version: 1.4.6
	Operating System: Windows 8 (amd64) version 6.2
	Java Version: 1.7.0_09, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 287121360 bytes (273 MB) / 519962624 bytes (495 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	AABB Pool Size: 3673 (205688 bytes; 0 MB) allocated, 3371 (188776 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 71
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 848 (47488 bytes; 0 MB) allocated, 797 (44632 bytes; 0 MB) used
	Player Count: 1 / 8; [iq['Verenos'/46500, l='Vesywor', x=-117.61, y=64.00, z=-289.17]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.