Did you use PhysX? PhysX is only working right on NVIDIA Cards, not on ATI Cards. I know this problem, then I have the ATI HD 5970.... You must optimize the Physx engine, so that it work with a ATI Card..... But this can only the Pr0 programmers... I don't know whether you are one....
And sorry for my English

I hope it helps you ^^
EDIT: I see that you dont use the physX engine.... but if you use A8 you will get ptobably errors with the A7 physics engine....

good luck