Can you boot commandline (no gui) on the relevant install? Are we talking gnome?
If so then between these two links you should be able to sort things out:
http://askubuntu.com/questions/17249...e-gconf-editor
http://ubuntuforums.org/showpost.php...86&postcount=4 (http://ubuntuforums.org/showthread.php?t=1723321)


