Someone (I no longer have the original) wrote:
<snip re: gdm not starting although startx works>
I played with gdm the other day, and found that if the standard greeter is used, gdm worked fine, but if I used the graphical greeter, I saw the same behavoiur of gdm trying to start 3 or 4 times and then eventually giving up.
I no longer have that machine in front of me, but the config file was something like /etc/gdm/gdm.conf, and the line that needs changing is something like "greeter=gdmlogin" as opposed to something like "greeter=gdmgraphical". The config file is pretty well documented, so you should be able to find it. Or you can just use "startx" to go into Gnome and then run the "GDM Configurator" ("sudo gdmsetup") and change it in that GUI tool.
-- Kent