gnome install: stuck

[n dhert]

Laptop with Freebsd 8.0, with gnome installed and
gdm_enable="YES"
gnome_enable="YES"
in /etc/rc.conf, no changes to /etc/ttys (that is: ttyv8 ... xdm off)
After reboot, system starts in gnome, gives a greenish background,
a taskbar at the bottom, with only date/time, a button for 'Universal
access preferences'  and an icon for the battery.
In the desktop a grey window with 2 buttons labeled 'Restart' and
'Shutdown'.
Clicking either of them makes them be blueish for the time the mouse
button in pressed, but nothing happens.
I am stuck in Gnome. Why and how to solve it ?

(I can only do Ctrl-Alt-F1 to get to the command prompt, but even that
I have to do twice: the first time it gives a flickering almost entirely
black
screen with at the top some half line of flickering ascii characters (can't
read), doing a Ctrl-Alt-F9 (back to gnome) and again Ctrl-Alt-F1 gives me a
stable login: prompt.)