There does not seem to be a way to properly access the gdm setup tool in dapper. If I choose the "configure gdm" option it asks me for a password, then if I type in my primary user account password it tells me it is invalid. I manually set a root password, and if I use it when it asks me for my password, gdmsetup pops up for a second then closes. I assume this is because it is set by default to disallow you from logging in as root with GDM, so in effect there is no way to get to it from here. I can access gdmsetup from within gnome via the commandline, but not at just the gdm screen. It also seems the icon for it has been removed from the default administration menu, so I would imagine this would make it very hard for a novice user to configure it.
My expected results would be for gdmsetup to use my primary user account's password as there is no known root account by default in Ubuntu.
Thanks for your bug. Please describe only one issue by ticket, you list differents one here: user password no working, window closing, gdmsetup icon (which is not masked, it's to system, administration) which have different settings, priorities, people work on, etc