Michel

You can only genlock the signal coming into the mac... but as yet you can't genlock to the mac.
Genlocking the signal via a switcher (grass valley/ross) is the only way I have done it, with multiple signal inputs. In truth though I have in not had any genlock issues via catalyst.

With your latency issue I would suggest you try the same test with the system you are using for the show. How many frames do you think you are loosing in the signal path? I find in Arena shows you can get away with 8 frames without it feeling too uncomfortable.
What is in the signal path to and from the catalyst? You mentioned a DVI fiber, I assume there are no DVI extenders in the signal path.

Phil