Problème Minecraft Optifine Ultra

Bonjour,



J'ai un problème avec un mod bien connu de minecraft, Optifine Ultra.
A chaque fois que je veux lancer le jeu en solo, il y a 90% de chances
que ça se bloque à "Téléchargement du terrain", sinon il crash juste après. Ensuite il m'ouvre un rapport:
Minecraft has crashed!
----------------------

Minecraft has stopped running because it encountered a problem; Exception in server tick loop

A full error report has been saved to C:\Users\Raphaël\AppData\Roaming\.minecraft\crash-reports\crash-2013-03-03_10.30.49-server.txt - Please include a copy of that file (Not this screen!) if you report this crash to anyone; without it, they will not be able to help fix the crash :(



--- BEGIN ERROR REPORT e4c3d352 --------
Full report at:
C:\Users\Raphaël\AppData\Roaming\.minecraft\crash-reports\crash-2013-03-03_10.30.49-server.txt
Please show that file to Mojang, NOT just this screen!

Generated 03/03/13 10:31

-- System Details --
Details:
Minecraft Version: 1.4.7
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.7.0_10, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 119479568 bytes (113 MB) / 954466304 bytes (910 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -Xms512m -Xmx1024m
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Suspicious classes: ~~ERROR~~ OutOfMemoryError: GC overhead limit exceeded
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Player Count: 1 / 8; [iq['Wims2O'/0, l='Nail by Whiskey Brigade', x=927,27, y=82,50, z=939,74]]
Type: Integrated Server (map_client.txt)
Is Modded: Very likely; Jar signature invalidated

java.lang.OutOfMemoryError: GC overhead limit exceeded
at bo.a(SourceFile:27)
at cd.b(SourceFile:96)
at bq.a(SourceFile:34)
at by.a(SourceFile:38)
at cd.b(SourceFile:96)
at bq.a(SourceFile:34)
at cd.b(SourceFile:96)
at bq.a(SourceFile:34)
at cd.b(SourceFile:96)
at ca.a(SourceFile:75)
at aam.a(SourceFile:54)
at im.f(SourceFile:125)
at im.c(SourceFile:76)
at il.<init>(PlayerInstance.java:47)
at ik.getOrCreateChunkWatcher(PlayerManager.java:167)
at ik.a(PlayerManager.java:157)
at ik.a(PlayerManager.java:206)
at gm.a(SourceFile:104)
at gm.c(SourceFile:147)
at gm.a(SourceFile:81)
at bec.b(SourceFile:73)
at net.minecraft.server.MinecraftServer.r(SourceFile:762)
at net.minecraft.server.MinecraftServer.q(SourceFile:679)
at bdz.q(IntegratedServer.java:170)
at net.minecraft.server.MinecraftServer.run(SourceFile:613)
at fy.run(SourceFile:849)
--- END ERROR REPORT 50f93a5b ----------

puis plus rien.
En multijoueur Optifine marche très bien, mais lorsque je n'ai pas de connexion je ne peux pas jouer vu que le solo ne marche pas.
J'ai installé Optifine avec Pipix.
En passant le mod Rei's Minimap ne fonctionne pas non plus, chargeant au lancement de minecraft, l'écran clignote puis deviens noir. A cause de ce mod je dois remettre un .minecraft ce qui me supprime tout ce que j'ai enregistré...
Ma config: Windows 8(c'est peut-être à cause de ça) 64bits
Carte Graphique: NVIDIA GEFORCE GTX 670M 3GB
Processeur:Intel Core I7 2,40GHZ
Ram: 8GB
Ma version de Java est également à jour..
Quelqu'un pourrait-il m'aider à résoudre mon problème?