You updated to the latest BIOS revision, correct?
Okay, there is another possible workaround for this. The problem is that the Steam DRM for this particular game and a few other titles does not agree with the FX CPUs for some reason. Go here
and download and run the program at the start of the thread. It is an unofficial fix that was used to get the game running properly before BIOS updates were available for the AM3+ motherboards. Hopefully that will fix your problem.