I've tried it on two different video cards. On a X1950 Pro the game runs at warp speed and on my old Geforce4 the game seems to fluctuate based on the frame rate. I was able to get the X1950 Pro to work at what I assume is normal speed by forcing vsync but that only worked with the 9.3 drivers and not the 10.2(newest available for that card). I haven't figured out anything to get the Geforce4 to work. The thing is, that's the card I originally played the demo on and I don't remember having these issues.

Do you have AMD dual core CPU ? If yes, then try AMD Dual Core Optimizer, perhaps problem is in there, not in the GPU units...:)

http://support.amd.com/us/Pages/dynamicDetails.aspx?ListID=c5cd2c08-1432-4756-aafa-4d9dc646342f&ItemID=153

Nope, I have an AMD single core.

Normally FPS shouldn't have effects like this, as it only affects the physics of this game to some degree, but you could try limiting the FPS with /setmaxfps command.