I've just upgraded Ubuntu from 12.10 to 13.04 under the latest release of Parallels 8 on a MacBook Air running 10.8.3 On the first reboot after upgrade I had the side bar but the main screen was black. I disabled 3D acceleration under the VM settings and rebooted to just the desktop with a parallels folder (no side bar or menu). I then was able to reinstall Parallel Tools from terminal, which normally fixes things, and rebooted the VM. No dice. Enabled 3D acceleration - same problem. Any pointers?