it sometimes happens me. only since i got a 2nd monitor though. i have the hd 3870 (@ 830/1241) and sometimes i get the error. i usually play games all day, part time jobs give me hours to spend sitting at the command center haha.
when gaming it can pop up aswell, i never had the problem as far as i can remember, it may have once or twice. have you OCed your card at all?
Now my HTPC will need WinXp 32. Bah. No Vista 64 for my 3850. Sapphire.
Pff. Better now than when i have everything rigged up and running.
I suspect thats a bit of an over reaction Ive known bad driver versions for both operating systems, I remember one version of nvidia drivers for xp that were an absolute disaster for some of the games I played... In fact the one of the earliest drivers I had for my 8800gtx gave me some very nasty graphics artifacts in oblivion rendering the game unplayable, that was one of the main games I got the card for it was fixed before long. I dont doubt this problem will be 8.6 seems stable enough under vista 64.