You can just delete your .gnome directory, this will reduce the amount of "recustomizing" you'll end up having to do. However, it may just be a glitch in the gdm (the startup/login manager) files. I believe those are located in /etc/X11/gdm but could very well be wrong as I've not started up into a gui for quite some time.
Here's the steps I'd start with, and then go from there:
Login from the command line as root.
cd into the users home directory:
Move the gnome directory to the root's home directory:
mv .gnome /root/gnome-sprice
And then try logging in again to see if that fixed it.
If you are using gnome2 the directory is gnome2