trouble adding window manager to GDM

[Philipp Bliedung <philipp.bliedung@furman.edu>]

Hello,

I am running Debian unstable and updated to Gnome 2.6 this past weekend. 
After the update (and an update to the newest version of gdm 2.4.4.7-3) 
I can't select any other window managers from the GDM login-screen.

I want to add blackbox and Xfce4.

I created a file named "Blackbox" in /etc/gdm/Sessions/ and added

exec /usr/bin/blackbox

I made this file executable (chmod 755), but when I log off and restart 
gdm I only have the same options I had before. I can't choose anything 
other that Gnome.

Any ideas?

Thanks a lot.
Philipp