Comment 1 for bug 381901

Hey! Thanks for taking the time to report this bug :).

When you boot ubuntu using the method that normally gives you a "blank desktop" at some stage you should have a menu with an option saying "recovery mode", select that and hit enter. If you can't find recovery mode, boot into the "blank desktop" and hit Ctrl+Alt+F6.

Now you should have a command line (black background, white writing). Log in (if it prompts you to), and then type:
init 2

That might sort your problem?