M-powered on Leopard: weird graphic errors and sluggish AS
 

Dunno whether the problems I have are related to:
- Leopard
- M-Powered
- Quad machine

I have a brand new 2 x 2.8 Quad Pro stuffed with 10g memory and a cleanly installed Leopard. I work on location abroad, so in this case I use a FW410 with M-Powered.
I'm fiddling around in a 24/44 session with pretty much nothing going on and no other apps running in the bg. than Thunderbird and Firefox I noticed weird screen redraws and blank windows when switching from e.g. Firefox back into PT: see here
And also Audiosuite is really sluggish, to the point of unworkable: whether I choose Z-Noise or Analog Channel.
I have set the Playback Engine to 256, 6 cores for RTAS and 85% CPU.
Trashed DAE,- and PT-prefs, I have no 'non-Leopard plugs installed (did a clean install of the whole machine... ouch!). Also removed some wrapped VST-plugs, but no change

Although I'm a very experienced user, I'm quite new to both Mac Pro and Leopard, so I hope these problems are related to the new machine and sw-environment, something a future maintenance-release might fix....

Anyone else got any idea's or suggestions?

I would possibly suspect bad RAM - have you tried removing some to see if the behavior changes?

What about testing from a new admin account?