Yes it definitely sounds like a driver issue to me...
Follow Astro's advice and if that doesn't help I would try and do a system restore to a point where your PC was working fine, uninstall all the current drivers, Clean your registry with a program like CCleaner (Clicky)
and install the most up to date drivers for the Graphics Card.
Also, what Graphics Card did you have before that? Did you check to make sure your Power Supply can handle this new one?