I purchased iMovie to try if I get same issue, and I do... Wasted $15...
All ports are FW400. And yes: I had tried to make sure only device plugged was the camera.
Again, it's not physical : same connexion work perfectly on same machine when under Windows. It most likely has to do with Mac OS X.
It's too bad as it now seems my only solution is to capture under Windows under CS 4 (create a project for nothing...) then switch to Mac OS X and edit the project under CS6 ! Talk about efficiency and productivity ! ... 
How many years (even decades) have I heard the ''Mac is better and easier for audio/visual'' .... Yeah! I now see it...