Originally Posted by nkalkhof
further more my screen turns black after dropping back from X (ctrl+alt+f1) but the system is still responsive. after blindly typing "startx", the X server comes back up again. this problem might be related to the stuck performance levels as far as I've seen in all the other posts.
If you haven't tried uvesafb yet, it might be worth a shot. I had a similar problem with my card and it did the trick. Moreover, it supports more resolutions, e.g. 1920x1200.
Unfortunately, downclocking is not as easy to overcome. Bug report for 8800M GTX.