I just upgraded to the Natty beta and I’m getting this error message every time I try to log in.
Failed to load session “ubuntu”
I have tried using every session available: Ubuntu, Classic Ubuntu, Unity-2d, and Gnome Shell. The only one that allows me to log in is Gnome Shell, but it doesn’t actually load Gnome Shell; it loads a gnome panel, but compositing/compiz doesn’t work.
I’m so confused, and I have no idea how to fix this or what is causing it. I would like to be able to try out Unity, but none of the sessions work except for this false Gnome Shell session.
Well, I have no idea what caused this… but it seems to have been some kind of package dependency problem. The packages were all a mess and I ended up just uninstalling and reinstalling everything and now it’s working.
source : ubuntuforums.org