Hook crashes the game while joining

After some experience in hacking CrossFire, I wanted to start hacking Combat Arms, so I first made a Direct3D hook.

The problem is, when I join a game while the hook runs, the game crashes.
I hook where Combat Arms calls DrawIndexedPrimitive and EndScene.
Is there a solution?

Thanks

hm it could be source, we can-not know for sure if we can help. Cause it may be your source. If it not your source it should work.
I suggest you post your source (If you dont want to, PM it to flameswor10 )

It just replaces
MOV ECX,DWORD PTR DS:[EAX]
MOV EDX,DWORD PTR DS:[ECX+0x148] (DIP)
with a Jump (0xE9 (Function) - (Hook + 5)) and NOPs (0x90);
I already tried to leave my function (almost) blank, but it didn't help.
Even this crashes the game :
__asm
{
MOV ECX,DWORD PTR DS:[EAX]
MOV EDX,DWORD PTR DS:[ECX+0x148]
JMP dipjmpback
}