i dont use 7's drivers, second i started i went to auzentechs webiste, XFX force, and so on to get my drivers.Probably like you said before, Windows 7 compatibility issue. I've gotten lots of compatibility issues with Windows 7 in multiple games of mine. Sh*t happens. I would still go ahead with Squeetard's suggestion.
Just a kinda lame troubleshooting suggestion, but this has helped for me, so I'm just going to throw it out there. When you install Windows 7 all or the vast majority of the hardware you have in your rig worked, right? Windows 7 has these pre-included drivers that are IMHO meant for basic operation of Windows 7, i.e. dragging around windows, glass effects, light 3D applications, etc. It works with games and stuff, but not as good as the straight-up drivers from the vendors.
TL;DR: Download and make dang sure you do a right proper job of installing them so that it DOESNT use the Windows 7 drivers. This solved a few issues for me when I would get relatively frequent crashing in GTA San Andreas, GTA IV, and even CoD4.