Todd,
I tried the same thing last weekend, FCP5 kept turning off “All frames” so no video out. I had the Blackmagic 5.0 drivers installed, it just would work. If you try selecting “all frames” you may get video, but for me it kept turning itself off.
There were also terrible quality issues with type that I see many folks in here also have had. I re-installed Panther, all way too buggy for me at present.