FCP7 MacPro Radeon 5770 Playback Issues

I had a gen1 MacPro and needed to upgrade to be able to use 64bit applications so I got a new MacPro with a Radeon 5770 outputting to a 30" 2560x1600 monitor and 10.8.2.

FCP7 playback is not very good, it appears to have a lot of tears on the video as though it can't keep up with the frame rate.

Has anyone else experienced this? My OLD MacPro had a Radeon 3870 and it screamed, never had any issues with it.

I'm curious if anyone is using an MXO2 Mini with Mountain Lion?