Problème de crash.

Bonjour, aujourd’hui, j'ai eu un problème de crash. Je suis passer de la snapshot 14w08a a la version 1.6.4. Puis dés que je veux lancer mon monde, il me dit ceci :
---- Minecraft Crash Report ----
// Daisy, daisy...

Time: 01/03/14 16:49
Description: Reading NBT data

java.lang.ClassCastException: ck cannot be cast to cj
at by.d(SourceFile:120)
at ye.c(SourceFile:128)
at ye.a(SourceFile:75)
at ud.b(SourceFile:360)
at uf.a(SourceFile:579)
at jv.a(SourceFile:82)
at nn.f(SourceFile:1062)
at alq.b(SourceFile:170)
at hn.a(SourceFile:159)
at hn.a(SourceFile:54)
at blc.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.t(SourceFile:489)
at net.minecraft.server.MinecraftServer.s(SourceFile:406)
at bkz.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:340)
at hi.run(SourceFile:583)


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

-- Corrupt NBT tag --
Details:
Tag type found: STRING
Tag type expected: SHORT
Tag name: id
Stacktrace:
at by.d(SourceFile:120)
at ye.c(SourceFile:128)
at ye.a(SourceFile:75)
at ud.b(SourceFile:360)
at uf.a(SourceFile:579)
at jv.a(SourceFile:82)

-- Entity being loaded --
Details:
Entity Type: null (jv)
Entity ID: 34
Entity Name: louislepetit54
Entity's Exact location: 177,53, 66,20, 115,84
Entity's Block location: World: (177,66,115), Chunk: (at 1,4,3 in 11,7; contains blocks 176,0,112 to 191,255,127), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0,00, 0,00, 0,00
Stacktrace:
at nn.f(SourceFile:1062)
at alq.b(SourceFile:170)
at hn.a(SourceFile:159)
at hn.a(SourceFile:54)
at blc.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.t(SourceFile:489)
at net.minecraft.server.MinecraftServer.s(SourceFile:406)
at bkz.s(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:340)
at hi.run(SourceFile:583)

-- System Details --
Details:
Minecraft Version: 1.6.4
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_13, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 51855936 bytes (49 MB) / 130940928 bytes (124 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 392 (21952 bytes; 0 MB) allocated, 392 (21952 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: 42 (2352 bytes; 0 MB) allocated, 42 (2352 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.