MAC OSX laggin when Parallels 5 is running

Hi,

i have a really annoying problem with parallels. My Host (OSX 10.6) and my guest (WIN XP / SP3) seem to lag
without any reason. They slow down, I see a spinning wheel and after 10 to 30 seconds everything works normal.
I experienced the same probs with Parallels 4 so I upgraded. Now it is even worse. Parallels Tools are new. Reinstall doesn´t help. Sometimes its even laggging when the guest is not up. It looks like the hdd is the problem.

Here the facts. Hardware: MBP 2,53, 4GB, 500 GB HDD 7200k.
Parallels 5
WIN XP SP 3

 

No one an idea?