I have noted that when a Virtual Machine is actively going to disk, the entire OSX machine can be left at a standstill. This means that any process that may be running (even a web browser, such as safari) can hang out waiting until that disk access slows down or stops within the VM. If you're running a 5 minute disk based process, it can take 5 minutes for anything on the OSX side to come back alive again. There should be a knob for controlling disk access priority -- it seems that Parallels may be sacrificing OSX disk access for parallels VM performance. Golan.