I have attempted to upgrade my Ubuntu 12.10 to 13.04 over a few download sessions. When I open Ubuntu 12.10 there is a pure white screen with only the cursor moving when prompted. I can access Terminal with Ctrl Alt F1 only. I don't think the download sessions were completed due to a very slow network. I've tried a number of commands to reinstall Unity and Gnome but no luck. I've read this could be a Unity or Nvidia or Compiz issue.