Mon Minecraft plante après 2 secondes de jeu

Bonjour, j'ai un petit souci concernant le jeu minecraft, en effet, dès que je lance une partie (qui se lance) le jeu plante au bout de 2 minutes, j'ai installé forge et optifine.
Voici le crash report :
---- Minecraft Crash Report ----
// My bad.

Time: 04/12/14 13:29
Description: Exception in server tick loop

java.lang.NullPointerException: Exception in server tick loop
at net.minecraftforge.common.ForgeChunkManager.saveWorld(ForgeChunkManager.java:836)
at net.minecraftforge.common.ForgeInternalHandler.onDimensionSave(ForgeInternalHandler.java:70)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_2_ForgeInternalHandler_onDimensionSave_Save.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122)
at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:820)
at net.minecraft.server.MinecraftServer.func_71267_a(MinecraftServer.java:308)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:180)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:670)


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

-- System Details --
Details:
Minecraft Version: 1.7.2
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_71, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 138814504 bytes (132 MB) / 354029568 bytes (337 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
AABB Pool Size: 7005 (392280 bytes; 0 MB) allocated, 3494 (195664 bytes; 0 MB) used
IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
FML: MCP v9.03 FML v7.2.217.1147 Minecraft Forge 10.12.2.1147 Optifine OptiFine_1.7.2_HD_U_A6 3 mods loaded, 3 mods active
mcp{9.03} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{7.2.217.1147} [Forge Mod Loader] (forge-1.7.2-10.12.2.1147.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{10.12.2.1147} [Minecraft Forge] (forge-1.7.2-10.12.2.1147.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1529 (85624 bytes; 0 MB) allocated, 1186 (66416 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['Azazel0056'/483, l='New World', x=238,50, y=64,00, z=249,50]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'