[colnago]

I had the same problem and it ended up being a third party application. I can't quite remember which one exaclty as I uninstalled all of them that I did not need. I know it is a pain, but you may have to spend some time trying this method. BTW it is the only time I have ever had a problem since I purchased my set-up over a year ago. I also made sure I ran everything USB related straight to the Mac.

Dual G4 1.25
Jaguar OSX
MBOX 6.1.2
Samson control room
Reason, Spectrasonics, Live, Amplitube, T-racks, Plugsound, and some Freebies.