I just want to reiterate Sgt AA's point. I appreciate this problem isn't down to the gamemaker, but if this game ever appears a huge chunk of people won't touch it with a barge-pole until this issue is resolved.
I have the same issue as well with a 8600GTS. Though the demo for Shock Force works fine. Guess I'll be fighting modern wars from now on. (weeps uncontrollably!)