Many players have reported strange graphical errors recently and we believe that this may have something to do with the most recent Nvidia Drivers.  Many people have reported similar errors with other games when using this most recent driver.

The older driver can be found here: http://www.nvidia.com/object/win7-winvista-64bit-275.33-whql-driver.html  Please try to rollback your driver to this earlier version to see if this corrects your problem.