Joss,
http://bugzilla.gnome.org/show_bug.cgi?id=524665 in Gnome Games on which you have commented appears to actually be this bug in disguise. It appears to happen because Ubuntu is packaging glchess in Universe in addition to gnome-games. As a result, some users are uninstalling glchess and installing gnome-games in the same apt transaction. When triggers runs, it appears that it gets confused when modules of the same name in the same directory are both being installed and uninstalled at the same time.
