I'm Windows, so none of this may help... but reading might help
Troubleshooting guide for Mac freeze
Is that a Retina?
Mac Retina Bug http://forums.adobe.com/thread/1159632
Mac and Root User http://forums.adobe.com/thread/879931
I dont think the issue is with the graphics card, as you mentioned that you have installed CUDA for MAC, which is the right think CUDA is developed by Nvidia and works just fine with your graphics card i.e. 650M. I suggest check the firewire interface again with which you are recording, you can also change your firewire cable as well.
Also are you using thunderbolt port for capturing?
I uninstalled Premiere and re-installed from the DVD. The version installed is 6.0.0. I tested capturing again and it worked fine with Mercury Playback ghosted out. I then installed the 6.0.2 update and Mercury Playback is now selectable. I tried capturing again and it worked fine. So it's something with the 6.0.4 update causing the problem, I'm just not sure what.
As to your question, I am capturing through the thunderbolt port. Though, again, it works fine under 6.0.0 and 6.0.2, just not 6.0.4 so there is something in that update the Mac and/or software doesn't like.