I have a very similar problem. I just installed my 3870 x2 over my 8800gt 512 and my 3Dmark06 score went from 12k to 10k. SM3.0 is "ok" at 5k but sm2.0 is only 3k. And for some reason my Phenom went from 3800 to 3000 flat. :-/ Used both 8.2 and 8.3 drivers with the same result. Both drivers were on fresh clean Vista 64bit installs. I did install SP1. The Proc is OC to 2.5Ghz from 2.3. Havent tried 2.6 yet to see if it is indeed the proc bottlenecking. We shall see. I also has dismal performance on games as well. About the same as the 8800GT even though it should spank it sideways.