Well, this is interesting. I tried the purge command to get rid of gnome-shell and got "Package gnome-shell is not installed so not removed." It seems like I'm getting the error about the gnome settings daemon even though gnome isn't installed.

Anyway, I tried to install gnome by doing:

sudo apt-get install gnome-shell

It did a bunch of stuff and then I rebooted. When I got back, the UI looked like it always did, so I don't know if I should have done something else to install gnome. Anyway, when I tried to shutdown using the menu option, I got the same old settings daemon message.

I'm totally befuddled. Any other suggestions?