w7 is so buggy, i recommend reinstalling vista if you have it. thats what i did. people are touting w7 as flawless but its far from true. vista works perfectly now whereas w7 is exactly like vista was at its launch.
frankly i didnt see any significant improvements over vista after installing windows 7
as far as your particular issue its no surprise at all. wish i could offer more than that but im a nvidia user and always have been.
Edit:
i did find this bit of info that may or may not help you. (google is your friend) at the bottom of the post is a fix that user did and it seemed to work for him/her give it a try and let us know
http://www.sevenforums.com/graphic-c...g-drivers.html