quad core compatibility issues

Alright all you people with quad core out there can you please tell me of any compatibility issues u may have encountered with games. COD:UO had a stuttering problem that i fixed by settings nhancer to single core for that game. I havnt tested cod2 but i have a feeling that its suffering from the same problem. Most new games run flawlessly with the exception of bioshock. It runs great on all drivers ive tested except (163.71). The only thing i noticed is that despite what driver i use when i am running through that scene where all the water burst into that place it will get stuttery if i continuosly stay in that area and jump around and stuff. Anyone else have this problem?
I have Q6600 @ 3.2ghz 2gb ddr2 890 5-5-5-12, 8800 GTS 640mb 670/1020, ABIT IP-35 PRO.