Hopper: java.lang.ClassCastException: asx cannot be cast to aox

java.lang.ClassCastException: asx cannot be cast to aox
	at aoy.<init>(SourceFile:33)
	at aox.a(SourceFile:372)
	at aox.a(SourceFile:334)
	at aez.a(SourceFile:453)
	at act.d(SourceFile:327)
	at akk.a(SourceFile:384)
	at akk.a(SourceFile:508)
	at aib.a(SourceFile:395)
	at akm.a(SourceFile:29)
	at akg.a(SourceFile:73)
	at agc.a(SourceFile:400)
	at kc.a(SourceFile:156)
	at aez.a(SourceFile:774)
	at kc.c(SourceFile:93)
	at kb.<init>(SourceFile:28)
	at ka.a(SourceFile:209)
	at ka.a(SourceFile:246)
	at hw.a(SourceFile:151)
	at hw.c(SourceFile:202)
	at hw.a(SourceFile:95)
	at bnq.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bnn.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hr.run(SourceFile:575)

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 06.09.13 15:21
Description: Exception in server tick loop

java.lang.ClassCastException: asx cannot be cast to aox
	at aoy.<init>(SourceFile:33)
	at aox.a(SourceFile:372)
	at aox.a(SourceFile:334)
	at aez.a(SourceFile:453)
	at act.d(SourceFile:327)
	at akk.a(SourceFile:384)
	at akk.a(SourceFile:508)
	at aib.a(SourceFile:395)
	at akm.a(SourceFile:29)
	at akg.a(SourceFile:73)
	at agc.a(SourceFile:400)
	at kc.a(SourceFile:156)
	at aez.a(SourceFile:774)
	at kc.c(SourceFile:93)
	at kb.<init>(SourceFile:28)
	at ka.a(SourceFile:209)
	at ka.a(SourceFile:246)
	at hw.a(SourceFile:151)
	at hw.c(SourceFile:202)
	at hw.a(SourceFile:95)
	at bnq.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bnn.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hr.run(SourceFile:575)


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

-- System Details --
Details:
	Minecraft Version: 13w36b
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 70635472 bytes (67 MB) / 168730624 bytes (160 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 959 (53704 bytes; 0 MB) allocated, 903 (50568 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 119 (6664 bytes; 0 MB) allocated, 119 (6664 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['stormtraxx'/64, l='snapshot', x=-123,47, y=70,15, z=-803,51]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.