I was having a similar problem with a Canon GL2. The solution was to go into sequence > sequence settings > playback settings…, and change the Realtime Playback and Export – External Device: from none to DV.
I remember on my old Sony digital 8 camcorder I used to have a lot of problems with firewire, and I think I remember reading that people who had Sony computers didn’t have the same problems. When I finally switched to Canon on the same computer the problems went away. If you are still stuck you might try to export to another camera.