Hi Will,
Sounds like your on the right track with Tech support regarding complete uninstalls (and trashing related remnants) and complete reinstalls.
But in terms of reliability I have an Mbox 2 Pro with an intel Macbook here and the performance is really great (playback of real heavy sessions @ 64 samples with 2 RTAS processors loaded with plugs even off the internal drive). I've tried to break this setup (within reason..not the app reason, but within reasonable expectations -and I'm good at breakin' things ) and it is bulletproof thus far.
However, at first, I was seeming to get sporadic results unless I had the Macbook plugged in (underpowered firewire?) in both 10.4.6 and Bootcamp (Bootcamp I think is still a little risky). I initially had the stock 512k RAM but then maxed it out to the 2 gig and thus far with it plugged in or not the performance is amazing. I have to install the PT cs update for Mbox 2 Pro but again I can't say enough about how this has been working for me.
Just thought I'd mention the power and RAM situation I encountered (I'm not saying this is related to your issues and/or would fix your setup), but with that Macbook Pro you should be getting amazing results like I am.. and I only have the Macbook 2ghz dual.
Oh one last thing.. somewhere I installed an incompatible (with Intel Mac) plug-in (or software) that made my screen resolution all funny (looked like a crayon painting). I had to reinstall Tiger (painfully slow) and since this machine (along with Mbox 2 pro) continues to excite me.
Hang in there and good luck!
leonard
www.labranville.com