I upgraded directly from 3.0 to 4.0 but when I try to run PD, it hangs on startup. The icon bounces for a long time before settling down and doing nothing. Checking the Activity Monitor, both Parallels Desktop and Parallels Starter are hung and are not responding. The application name never appears in the title bar and no windows ever show up. I tried uninstalling it, reinstalling it, uninstalling it, deleting all traces I could find including preference files, and reinstalling it, all with restarts or shutdowns in between. It still behaves in exactly the same way. It hangs on startup and refuses to proceed.