I believe I have a similar problem to what is described here (though not all symptoms appear identical). When loggin in on my Gnome session, the only thing I get is a black screen and a (functional) mouse cursor. 'ps' in a terminal shows that only x-window-manager, ssh-agend, dbus-lauch & -daemon and gconfd-2 have started. Nothing else appears to be happening. If I log in on the Failsafe Gnome session, I get a functional desktop with all the usual bells and whistles (except my 'Controls' theme isn't loaded). But the GNOME Settings daemon gives the 'Unable to determine the address of the message bus (try 'man dbus-launch'...' error. Similar errors appear when opening (some/many?) of the preferences dialogs.
Hope this report will help the 'Needs Info' status... ;-) ** Attachment added: "gnome-settings-daemon-bugreport.txt" http://librarian.launchpad.net/6897581/gnome-settings-daemon-bugreport.txt -- gnome-settings-daemon crashes at login https://launchpad.net/bugs/61381 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs