I think this is because you have not installed python-gtk2 which gnat-gps recommends. Please try again after installing python-gtk2 and tell me whether this solves the problem.
[the reason gnat-gps recommends but does not depend on python-gtk2 is because, without python-gtk2, most of the functionality in GPS is still available; the only part affected is the graphical project editor as you discovered] Hope this helps -- Ludovic Brenta. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org