Hi,

When /tmp is not writable, GDM will fail to start a login
session in a bogus way. It will directly come back to the
same screen without any error indication.

I think it's important to tell about it, because otherwise
hunting down the problem can be a nightmare.

I experienced this problem a couple of days ago when my /tmp permissions
where incorrect.

This is not a problem with gdm. gdm starts fine. It is just that
gnome-session (or whatever gdm forks) can't start. The problem is there;
gdm is just telling what it is supposed to do: fork another application
once the user hits the "Log in" button.

I'd close or re-assign this bug.

Cheers,

Eloy.-