I was also having problems with my 7900gt. Everytime I came out of sleep mode the screen would get all scrambled. Reinstalled microsft drivers and all is well. Havent tried to run any games yet though.
there is definitly something up with the power modes and nvidia drivers. Im just happy the microsoft drivers are working right now.
When you say power-modes, do you mean that cpu-throttling causes graphics distortions and a hard lockup? If so I have an open bug you should validate and comment on. It's been open for a few months now so I really hope you're on connect.
Hmm I'm not on connect for vista (wish I was)
but what I see seems to be the OS sending like a "go to sleep mode" or simmilar message and the driver then trashing the screen and locking the pc.
it might be some other issue that's just my guess.
video playing and no keyb or mouse io for about 3-5 minutes and BOOM!
later I'll look at my vista perf settings and see if chnaging them alters this ...