That system should easily run it. It seems very bizarre. One thing I do know is that some graphics cards did have issues with the sim when it was first released, however, I also know that some of the minimum required specs are not actually required at all, for example, pixel shader 2.0 is listed as a minimum requirement on my boxed (German) XP copy, and that's not true at all, it runs on one of my laptops with just simple on-board graphics and Vista rather than XP, so the minimum specs are not even required judging by that. I think a lot of that is to do with the fact that it got chopped down a bit in development and released in a less ambitious form.
With that in mind, one thing you might try is an older version of the Catalyst drivers, I did notice SOF was a bit choppy on my desktop with the latest Catalyst drivers (not the only 3D application to suffer that either), which I've since binned off and dropped back to earlier ones. Might be worth a shot, unless of course you've already tried it. Reloading direct X is always another favourite to try.
Chock