i seriously doubt it has anything to do with physx. the fact is, nvidia has a much stronger developer relations program than ati does. that's why most games work just fine with nvidia out of the box, because they have a lot of testing and dev support going on through the development. ati has been caught out quite a few times when it comes to dev rel.
more importantly, you have to remember that the developers (pandemic studios) were fired a few weeks before the game released. this must have certainly affected the testing and final coding of the game. although i have to admit, it's beyond ridiculous that the game was completely unplayable on ati and whoever tested it missed this. worst software testing of the decade award goes to... :tongue: