What driver revision are you using?
Using latest, 304.18,
this makes games like Tribes Ascend almost unplayable. I tried disabling VSync and Frame Rate Stabilizer in hopes of doing something but nothing worked. Other games are smooth and fine. This also happens on APB Reloaded which removes my thought that something wasnt working in Unreal Engine along with my card. Anyways any help would be appreciated. I can't imagine somethings wrong with the actual card since other things work fine.