Why you don't use Fusion? We use a lot it also with multiple machine opened at the same time on our MacBook Pro. Sometime we just stop the OS without suspending the VM and after that everything is still working fine...Fusion is really a great product. - Alan Lugiai

Hope to test soon the rel. 3 ;-) - Alan Lugiai

Yeah, I'm gonna switch when I get a copy. I made the mistake of paying for parallels, and got suckered into paying for upgrades every year, parallels 2->3->4. A total dollar auction. - Ray Cromwell

Hm. Parallels and vmware both use the virtualization stuff built into your CPU and some clever but simple passthroughs for other devices. Crashes are more likely indicative of failing hardware. You can try virtualbox to see if it does the same thing. Be sure to uninstall parallels first (don't delete your image, you just want to get rid of the parallels kernel extensions) - mjc

After writing my post I tested the rel. 3 of Fusion yesterday. Seems faster then the old one...they say that it fully support Snow Leopard and is entirely 64bit... - Alan Lugiai

Yes, they both use the VT-x stuff, but I think the crashes might come in some of the virtual device driver stuff, e.g. mapping gfx calls to OSX. This was definitely the case with 3d support. - Ray Cromwell