I thought I would add... I don't know if it is related or not, but has been a problem for just as long, and despite my changes in drivers or ram: the opening movie skips and the sound separates out from it and plays faster than the video. The longer it plays, the worse it gets until the sound ends a long time before the visuals.

Don't know if that's a symptom of the same problem, or what.
This issue is frustrating. I've read so much on it, and really feel like it shouldn't be acting quite like this, especially with it never getting more performance even in full screen or anything.
Playing tonight, it was averaging around 15 fps in most areas, no matter my resolution settings or windowed/full screen, etc, and with everything off.
Monitor says cpu maxed at 100% usage overall. Most either core varies is a few percent. I don't know how normal that is for this game...