I'm having the same problem.
Both my full Mocha and the Mocha AE that shipped with Adobe CS4 import 1920x1080 23.976 Uncompressed 4:2:2 Quicktimes exported from FCP 6.05 and displays only a black view screen. I made sure I didn't have a bunch of apps open when I tried.
I'm running OSX 10.5.7 on a 15" MacBook Pro 4GB
Mocha AE 1.22
I loaded some SD material and Mocha worked fine.
I will try the Animation codec, but I really need it to work with HD uncompressed.