Hopper: java.lang.ClassCastException: mj cannot be cast to jh

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-318871/

Crash:

java.lang.ClassCastException: mj cannot be cast to jh
	at ji.a(SourceFile:10)
	at ek.a(SourceFile:146)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 10/12/13 10:18 AM
Description: Ticking memory connection

java.lang.ClassCastException: mj cannot be cast to jh
	at ji.a(SourceFile:10)
	at ek.a(SourceFile:146)
	at ml.c(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:529)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at brh.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at kt.run(SourceFile:617)


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

-- Head --
Stacktrace:
	at ji.a(SourceFile:10)
	at ek.a(SourceFile:146)

-- Ticking connection --
Details:
	Connection: ek@42bdfa0e
Stacktrace:
	at ml.c(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:529)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at brh.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at kt.run(SourceFile:617)

-- System Details --
Details:
	Minecraft Version: 13w41b
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.6.0_23, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
	Memory: 134936128 bytes (128 MB) / 343212032 bytes (327 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 2866 (160496 bytes; 0 MB) allocated, 2866 (160496 bytes; 0 MB) used
	IntCache: cache: 2, tcache: 0, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 983 (55048 bytes; 0 MB) allocated, 972 (54432 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.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-318871/17239676/