I think this bug could be related to a failure in handling the Games sub-categories (as described in http://library.gnome.org/devel/menu-spec/#category-registry in Additional Categories table). Karmic's gnome-menu comes with Games-Logic sub-category enabled (check Alt+F1). If you disable it on preferences (alacarte), the issue seems to disappear.
I think this bug could be related to a failure in handling the Games sub-categories (as described in http:// library. gnome.org/ devel/menu- spec/#category- registry in Additional Categories table). Karmic's gnome-menu comes with Games-Logic sub-category enabled (check Alt+F1). If you disable it on preferences (alacarte), the issue seems to disappear.