Logic 8 freezes and unfreezes when moving plugins on screen?

Question

I have a problem with Logic.
When I move a plugin from one place to another on the screen, it will get "stuck", and the spinning wheel will appear for 20-40 seconds. Sometimes the graphic in the plugin doesn't get updated after this problem occurs. Its enough to change to another screenset and back, and it looks ok again - but the main problem here is the freezing during the time Logic "thinks".
Logic doesn't crash after this happens, it goes back to normal - but its very frustrating having to wait around 30 seconds just because I want to move a plugin.
Here are a few factors to rule out:
Activity monitor shows that mem, cpu and space is all very ok
The problem occurs with both my internal soundcard and my MOTU PCI-424
Latest drivers, versions of all software
The problem is present when using only native Logic plugins, so rule out 3rd party incompability.
Is there anyone else experiencing the same problem? Is there any log for when Logic is running that I can check? If the application would have crashed I could diagnose it, but Logic never crashes, it just freezes for a while.
The problem does not start from the beginning of a project - but when I have loaded a couple of plugs - even without editing anything in the project - it starts freezing up.
I am desperate for help, I invested a lot of money in my new Mac Pro solely for the reason to run Logic. I have contacted AppleCare but they haven't gotten back to me.
Config:
Standard configuration of the newest Mac Pro model, no non-apple memory added.
One extra harddrive, but Logic is installed on system disk.
Midiman Midisport 4x4 USB interface
MOTU PCI-424 with 192IO interface
Genelec 8240 with controller software (USB connected)
PowerMate USB volume-control

Answer 1

I just thought I'd report back and say that my machine has been at the technical support department at Jigsaw Systems (where I bought it from) for the last 8 days or so, and they can't work out what the problem is and they can't fix it.
Even worse than that is that they tried this 'Monty' trick with the Space Designers on every other brand new MacPro that they had (which was 3 machines) and found the same problem on all of them.
And they tried it with a variety of graphics cards including the new NVidia 8800 and it still did it, though apparantly not quite as bad with the 8800.
Their conclusion is that this problem is specific to Logic 8 and the new MacPros and you WILL encounter this problem if you use Logic 8 on a brand new MacPro.
The Apple / Emagic team had better find a fix for this quick.