What Window Manager are you using? Whenever I get gconf errors, I log using Gnome, then log out, and then log in with my preferred WM, which is Fluxbox. Try using a different Window manager to log into. If you do not have one, press ctrl-alt-f2 to open a console login screen, and see if you can login that way.
Rebooting just may fix the problem, but I hope the above gives you some things to try.