Just upgraded to 4.0. a boot camp partition. I didn't have to activate Windows again, the prl_vm_app constantly runs a 98%-99% cpu busy as shown in Activity monitor (it also has the Not Responding) flag set to. I don't remember this happening on the 3.0 version I had. It's doesn't seem to be causing a problem, both Windows XP and Mac OS are responsive, I'd even say the system (Mac OSX with Windows running) that it was with 3.0. Don't do much with Windows anymore, just a few apps that are Windows only left, just kind of wondering why the high CPU when Windows should be pretty much idle (nothing started within windows). I do have it set to have the adaptive hypervisor on, and weighted towards Mac OS programs if that makes any difference.