Subtle periodic digital pops on new iMac

[Pont68]

I just got a new i7 iMac (2.93ghz) and I loaded Protools 8.0.4. I'm getting slight digital pops periodically. I'm running a Digi002 rack with an external Seagate hard drive for audio. I don't have any 3rd party plugins except for Izotope (Ozone, Alloy, Trash, Spectrum all the latest versions), Steven Slate EX, EZ drummer. I'm concerned that the Kontakt 4 player (done all the optimizations) may be causing the issues. Does anyone know if you have to manually change if the 32bit or 64bit version loads? I saw an article on the NI forum on how to change which version loads but I can't find it anymore.