I'm on Ubuntu 12.04.2 and I normally use the classic desktop. Today when I first logged in I got an error saying something about a window manager has failed to start and has been disabled. Now no programs show up in the bar at the bottom. If I minimize a program it's just gone. Show/Hide Destop and the workspace switcher are still there, but nothing else. Furthermore, if I switch to the Unity desktop, the bar on the left no longe shows up either.

I've seen numerous other posts like this one http://ubuntuforums.org/showthread.php?t=1750010, but right clicking does nothing. Doesn't even bring up a menu anymore.

Any ideas? Thanks.