Phew, that was a close call! I rebooted and then I was able to choose a higher resolution 1366 x 768 and also I was able to restart compiz.
The only other strange thing was the little applets that live in the Gnome Panel at the top of the screen changed position, so I had to unlock them and move them around again.
I lost the separators on the panel also, and I cannot add a new one.
Other than that, everything seems to have returned to normal.