I'm running Ubuntu 12.04, and using gnome shell.
I've had my machine running for the last few days, and I've been installing updates as the update manager bugs me. I just rebooted, and now gnome won't start. I can use gnome classic and unity, but gnome 3 isn't working at all.
When I log in, the screen is black for maybe 20 seconds, but the cursor shows. Then, my wallpaper, but nothing else shows up.
I can get a terminal with ctrl+alt+t, and I tried to run gnome-shell, but it segfaulted.