More Digital Mixer Issues

[olliejohn]

Hi there.
This questions directed at anyone who may be any good at troubleshooting digital mixing desk issues as I've been helping a friend set up his new Tascam DM3200 (with firewire card), but I'm more of an analogue guy.
You might have noticed a couple of days ago I made a thread asking about setting up the DAW integration with this mixer - we finally managed to fix this issue after a phone conversation and an email to tascam, however, we've now got some audio issues going into the computer (I should add, my friend is using Logic Pro 9 on a Mac running Lion).
The problem is that we're getting this digital click every 5-10 seconds on pretty much every track, though it's worse on some that other - some are louder, and on some the click is more of a deafening buzz.
I've tried changing the clock settings, and we've spent literally days changing up the routing inside the mixer trying to get it working but to no avail.
Any info would be greatly appreciated,
Many thanks,
Ollie