Problem mit dem Server! ich brauche Hilfe

Wenn ich auf den Server joine ist alles noch ok, mein Spiel läuft flüssig, und, und, und, ...
doch wenn ich dann ein paar Minuten auf dem Server bin und rum laufe, kann ich mich nicht mehr bewegen für eine Zeit.
Und dann kommt bei mir: Minecraft has crashed!

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 31.05.13 13:14
Description: Unexpected error

java.lang.IllegalStateException: Already tesselating!
at bgd.b(Tessellator.java:555)
at bgd.b(Tessellator.java:545)
at bfy.a(RenderGlobal.java:1208)
at bfq.a(EntityRenderer.java:1551)
at bfq.b(EntityRenderer.java:1094)
at net.minecraft.client.Minecraft.K(SourceFile:597)
at net.minecraft.client.Minecraft.run(SourceFile:526)
at java.lang.Thread.run(Unknown Source)

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

-- Head --
Stacktrace:
at bgd.b(Tessellator.java:555)
at bgd.b(Tessellator.java:545)
at bfy.a(RenderGlobal.java:1208)
at bfq.a(EntityRenderer.java:1551)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [bdv['CaptainBasti'/5277173, l='MpServer', x=22,96, y=66,62, z=30,46]]
Chunk stats: MultiplayerChunkCache: 225
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-720,61,747), Chunk: (at 0,3,11 in -45,46; contains blocks -720,0,736 to -705,255,751), Region: (-2,1; contains chunks -64,32 to -33,63, blocks -1024,0,512 to -513,255,1023)
Level time: 256184863 game time, 257847197 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 13 total; [np['Gemälde'/522, l='MpServer', x=55,06, y=67,00, z=47,00], np['Gemälde'/530, l='MpServer', x=55,06, y=72,00, z=50,00], bdv['CaptainBasti'/5277173, l='MpServer', x=22,96, y=66,62, z=30,46], np['Gemälde'/531, l='MpServer', x=61,94, y=68,50, z=50,00], nf['entity.ItemFrame.name'/519, l='MpServer', x=54,50, y=67,50, z=30,06], np['Gemälde'/522, l='MpServer', x=55,06, y=67,00, z=47,00], nf['entity.ItemFrame.name'/526, l='MpServer', x=56,50, y=67,50, z=37,94], nf['entity.ItemFrame.name'/527, l='MpServer', x=54,50, y=67,50, z=37,94], np['Gemälde'/530, l='MpServer', x=55,06, y=72,00, z=50,00], np['Gemälde'/522, l='MpServer', x=55,06, y=67,00, z=47,00], np['Gemälde'/530, l='MpServer', x=55,06, y=72,00, z=50,00], np['Gemälde'/522, l='MpServer', x=55,06, y=67,00, z=47,00], np['Gemälde'/530, l='MpServer', x=55,06, y=72,00, z=50,00]]
Retry entities: 0 total; []
Stacktrace:
at bds.a(SourceFile:282)
at net.minecraft.client.Minecraft.b(SourceFile:1881)
at net.minecraft.client.Minecraft.run(SourceFile:540)
at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
Minecraft Version: 1.5.2
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.7.0_21, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 327529408 bytes (312 MB) / 509870080 bytes (486 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -Xms512m -Xmx1024m
AABB Pool Size: 510 (28560 bytes; 0 MB) allocated, 390 (21840 bytes; 0 MB) used
Suspicious classes: IWrUpdater, Config, WrUpdaterSmooth, ...]
IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
LWJGL: 2.4.2
OpenGL: GeForce GTX 660M/PCIe/SSE2 GL version 4.3.0, NVIDIA Corporation
Is Modded: Very likely; Jar signature invalidated
Type: Client (map_client.txt)
Texture Pack: faithful32pack.zip
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1163 (65128 bytes; 0 MB) allocated, 116 (6496 bytes; 0 MB) used

Minecraft neuinstallieren: hat nicht geklappt
Im Singleplayer spielen: hat geklappt
Auf anderen Servern zu joinen und rum zu laufen: hat geklappt