Squeeze with gdm3 - sessions menu missing from greeter
I'm running debian squeeze which came with gdm3. I have not attempted to customise gdm3 at all. At the login screen all I see is the username/password box, and a few things at the bottom right of the screen (accessibility, the time, and the shutdown icon).
I want to have the sessions menu on there so that I can choose between gnome and dwm. The desktop files are present as you can see (gnome and twm were there by default and the dwm one was put there automatically when I did "aptitude install dwm").
root@blackbox:~# ls /usr/share/xsessions/
dwm.desktop gnome.desktop twm.desktop
Why am I not seeing a sessions menu? And how do I get one? I have trawled google and no-one else seems to have this problem, so am I just misunderstanding something?
Thanks in advance