Not sure. But It may be a similar issue that had ATI users pulling their hair out with FC2. Had to either run in DX9 mode instead of DX10. Or edit the inf to force a cap limit to 30FPS. You may want to try the cap limit trick if you can.
Edit: Try
this driver as well. Be sure to remove your old driver in control panel, resart in safe mode and use a tool such as
Driver Sweeper to clean any remnants and registry entries up. Restart in normal mode and install the new driver.
I also read that you can select render ahead settings. Try setting to 2 or 3. If that doesn't help put it back to the default. Hope you get it sorted out!