I encountered this trouble on a laptop upgraded from precise to quantal (linux 3.5.0-19). Using previous linux version (3.2 from precise) or 3.6 from PPA didn't helped. After backuping and removing ~/.{compiz,config,gconf{,d},gnome2} directories, it now works normally. I haven't find the main trouble yet.
I encountered this trouble on a laptop upgraded from precise to quantal (linux 3.5.0-19). Using previous linux version (3.2 from precise) or 3.6 from PPA didn't helped. After backuping and removing ~/.{compiz, config, gconf{, d},gnome2} directories, it now works normally. I haven't find the main trouble yet.