I don't remember where I saw it - I think on a kiosk howto - but I
think there is a way to disable an account from being able to open a
shell.
I don't remember how it was accomplished - I think something was
installed that would watch for instances of gnome-terminal and xterm
etc. spawned by the user and kill them when started.
You might be able to put something in the .bashrc that would kill the
shell - but that would I think prevent the gui from staring as well.
