Look for a report named AppCrash_BatmanAC.exe . Open the Report.wer file. If you see Exception code: 0xc0000005 , that is a memory access violation (Fix 1 or 3). If you see Fault Module: nvphysx.dll , that is the PhysX conflict (Fix 2).
Navigate to your Documents folder and delete the entire Batman Arkham City GOTY or WB Games folder. Look for a report named AppCrash_BatmanAC