Recently playing with Ubuntu 11.04 Unity desktop. Tweaking some of my work around, I found this quite helpful 'Things to Tweak after Installing Ubuntu 11.04 Natty-Narwhal Unity desktop'.
I come up to play with compiz settings and kinda set things up accordingly for a test. Suddenly I messed it up and 'unity desktop' is gone, no side bars and top panel.
And so, I tried to make another user from Ctrl-Alt-F1, login as root
# adduser 'newuser'
# passwd newuser
Well eventually it works out fine, but I have to reconfigure everything I built under that profile like browser settings, plugins, etc.
Inorder to recover everything back, I found this solutions from http://ubuntu4beginners.blogspot.com/2011/04/missing-top-and-side-panels-in-unity. http://ubuntu4beginners.blogspot.com/2011/04/missing-top-and-side-panels-in-unity.html