2x Radeon 6850 cards in 10.7.1

[foodfightr]

I'm running 10.7.1 without any problems using a Radeon 6850. I recently purchased a second Radeon 6850 with the hope of adding more displays. With both cards the system hangs during boot at the gray Apple screen. It's safe to say there is no problem with the mobo/card/psu as Windows boots fine.

I tried booting with GraphicsEnabler=Yes which didn't change anything.

Any idea how to get this working? Thanks