The OFB read me file says its a problem with the 6 series cards specifically and I use a GEForce 6800 GT. I have heard that using older drivers improves things slightly but the game still crashes in the end, it just takes 15 minutes longer to get to that point. I had graphics problems with Nightlife so I don't know why Im even vaguely surprised by all the trouble OFB is causing me!
I've decide that Im going to admit defeat and wait for my copy of Elder Scrolls Oblivion to arrive and play that instead. Damn Maxis and their crappy game to hell I say.