might sound like a shot in the dark, but sometimes a defrag will fix gaming issues. Dirt 2 crashed my pc twice but after a defrag it was fine. Also when batman came out i played it no problems with 64 bit, i think that was Nvidia 190.xx or 195.xx drivers so maybe try those.
If you suspect physx you can try downloading the pc demo, it does not have physx. (i think its like a 2gb dl)