When I logout or shutdown the terminal (the one I reach with Ctrl Alt + F7) is sometimes shown before the login screen appears or before the computer is shut off. Is there a way to stop this behavior?

More explicitly. If I logout the terminal is sometimes shown for a second before the login screen appears. Also, sometimes when I shutdown (from within Unity or Gnome) the terminal is shown, sometimes for the whole shutdown process or just for a second or two.

I've had this problem throughout 10.04, 10.10 and 11.04 and I've always used the standard Ubuntu variant. I've also noticed this happening on a fresh install of Natty on a friends netbook, so it's not local to my computers.