Yeah, I'm running the latest ATI drivers, with DX10.1. My machine's specs are:
Gigabyte GA-EP45-DS3 Intel P45
ATI Radeon 4870X2
8 gig RAM
Intel Core 2 Quad Q9550 LGA775 'Yorkfield' 2.83GHz
It must be something to do with the dual core GFX card, as that's the only common factor between our machines.