This problem is very weird, and no amount of googling showed any other similar case.
I emerged GDM (along with GNOME 2.22) on my Gentoo Linux installation and after I restart to see it in effect I met with this nasty irritant:
It comes each time one logs in, automatic or not, after the password is entered. Only if you click the OK button does it go ahead and proceed with the login.
After around 3 hours of madness googling for at least ONE person with a similar case or fix, I got fed up and gave up.
But the entire search time was not futile since I found this page which said that during a boot process, and after login, the /var/log/lastlog file is checked and if found, is displayed.
So I removed /var/log/lastlog and tried a re-login and amazingly enough this dialog box didn’t show up.
Thus, I added the line
rm /var/log/lastlog to my GDM init.d script before its first start line and that seemed to have fixed this irritating issue, not in a good default way though, more like a counter hack.
(P.s. I made that window shot shown here, since I could not capture the screen while GDM showed it.)
Any ‘actual’ fixes to it? My DisplayLastLogin variable is already set to false in the gdm.conf, but to no effect.