We are very sorry.
This problem affects the 8 core MacPro when using the default hyperthreading.
There is an update for CS4 (9.0.2) but not for CS3 I’m afraid.
Quick solution, install CHUD tools (from Apple) and turn off hyperthreading. (have not heard anyone mention any noticeable performance loss)
Or you could upgrade to CS4 or Cycore Effects HD, either will cost though.
Don’t hesitate to contact our support if you have any questions.