Ok so the problem that has plagued myself and a handful of other users over the past few months goes like this : It seems to affect 5 series crossfire users, particularly 5850 crossfire from what i've seen. the problem: Heaven 2.0 bench crashes after seconds of it being run - only with tessellation enabled Stone giant demo crashing with tessellation enabled Dirt 2 freezing whenever crowd is set to ultra. if you're experiencing this you'll probably find this also : heaven 1.0 works fine with tessellation AvP works fine with tessellation Heaven 2.0 works fine too - if you IMMEDIATELY hit spacebar as you enter the bench and go free roam while tessellation is enabled. However if the bench runs it's usual loop it'll freeze usually at the end of the pathway in the first scene, but sometimes goes to the 2nd or 3rd scene before it locks up. You'll also find that if you disable catai and inturn turn off crossfire ALL of these games and benches work fine with whatever levels of tessellation you like. What has worked for me and a few others in this thread : http://forums.guru3d.com/showthread.php?t=319171&page=3 What I did was I removed both of my reference 5850 cards and simply switched the slave card to the masters position and vice versa - simply swapped the cards around. now this alone could be what fixed it, but I also changed the orientation of my crossfire bridges too So if you're experiencing any of these symptoms above please give this a go. It's worked for a few of us but not all. Another guy who had this problem found that in his trifire set up that everything worked fine running two cards but as soon as trifire was enabled he was experiencing this tessellation issue too. In his case he had 2x reference sapphire 5850 cards and then added a non reference 5850 and then this started happening. He unfortunately RMA'd his non reference card to get another reference sapphire 5850 before we found out that swapping the cards around seems to fix it for a few of us. So again, if this is happening to you give this a try. Hopefully no RMA required. I just wanted to let everyone know about this because its been annoying the hell out of myself and quite a few others including paulieg who started a thread about it here a few months back (hope this works for you man) Anyway, give it a try if this is happening to you Cheers.