Hopper: java.lang.ClassCastException: mp cannot be cast to ji

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-402117/

Crash:

java.lang.ClassCastException: mp cannot be cast to ji
	at jj.a(SourceFile:10)
	at el.a(SourceFile:145)

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

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 19.10.2013 4:02
Description: Ticking memory connection

java.lang.ClassCastException: mp cannot be cast to ji
	at jj.a(SourceFile:10)
	at el.a(SourceFile:145)
	at mr.c(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:529)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsb.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at kx.run(SourceFile:617)


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

-- Head --
Stacktrace:
	at jj.a(SourceFile:10)
	at el.a(SourceFile:145)

-- Ticking connection --
Details:
	Connection: el@7808f016
Stacktrace:
	at mr.c(SourceFile:134)
	at net.minecraft.server.MinecraftServer.u(SourceFile:529)
	at net.minecraft.server.MinecraftServer.t(SourceFile:441)
	at bsb.t(SourceFile:117)
	at net.minecraft.server.MinecraftServer.run(SourceFile:358)
	at kx.run(SourceFile:617)

-- System Details --
Details:
	Minecraft Version: 13w42b
	Operating System: Windows NT (unknown) (amd64) version 6.2
	Java Version: 1.7.0, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 183316208 bytes (174 MB) / 470745088 bytes (448 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 951 (53256 bytes; 0 MB) allocated, 951 (53256 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 116 (6496 bytes; 0 MB) allocated, 112 (6272 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-402117/19256960/