I've upgraded to Gnome 3 on my Natty install on my MacBook Pro 5,1. I installed gnome-session and got around the .ICEauthority problem.
Now if I log into "Ubuntu Gnome Shell Desktop" it waits a bit and then it shows a nice graphical screen (with a picture of a sad monitor) saying:
Anyone know the cause of this?Code:Oh no! Something has gone wrong. A problem has occurred and the system can't recover. Please log out and try again. Log out