Ok, I kept my home directory, containing all the .gnome2, .gconf* etc. Maybe the source of the bug is contained therein. Grepping for "gnome-session" there did not dig up something "interesting".
-- Unable to start applications after suspend/hibernation https://launchpad.net/bugs/49221 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs