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:

(Windows Vista and Windows 7)
http://www.nvidia.com/object/win7-winvista-64bit-275.33-whql-driver.html 

(Windows XP)
http://www.nvidia.com/object/winxp-275.33-whql-driver.html
Please try to rollback your driver to this earlier version to see if this corrects your problem.

Cards known to have this problem include:

NVIDIA GeForce 6150SE nForce 430