Re-Install game and latest graphics drivers. Drivers first then uninstall game and re-install.
Get latest patches as well, bear in mind to patch them in order, also hope your download is quick as Far as I can remember there are 4 patches, 1.1.0 271mb 1.1.1 64mb 1.2.0 939mb and 1.3.0 939mb, best of luck.