Comment 8 for bug 773867

I also experienced this. I had the full Unity crash, and recovered with something like this - the key was "unity --reset"
http://ubuntu4beginners.blogspot.com/2011/04/missing-top-and-side-panels-in-unity.html
Then enabled desktop cube with these instructions, which was fine:
http://ubuntu4beginners.blogspot.com/2011/05/enable-desktop-cube-in-unity-ubuntu.html
Then checked "Notification" in ccsm, which crashed Unity. "sudo service gdm restart" fixed it. Then I enabled "Shift Switcher" and the menu bar got corrupted. Screenshot attached.

Interestingly, it displays correctly while rotating the cube, but reverts to garbage when the rotation ends.