http://www.sevenforums.com/graphic-c...-gt-220-a.html
All I could find that looked similar to your problem.
Seems to be a hardware related issue. :/ (I didn't read it all though)
As I've never bought a Nvidia GPU I can't give you much support myself.
But from what I heard Nvidia have better software than AMD and therefor a software problem should be very strange.
Could be a compatibility issue. If some other software don't like Nvidia's updates. (Guessing)
Yea, this might seem like a stupid question but I've made the mistake myself.
Have you uninstalled your current drivers before installing the new ones?
Oh, and I can confirm that atleast the drivers for the AMD Radeon 6990 SUCK BALLS!