GtkMenu doesn't recognize it's parents?

["Jim George" <jimgeorge gmail com>]

In glade, I created a window, with a vbox. In the vbox, I created a
menu bar (called "menubar"), then add a menu called "help" and a menu
item called "about", and set an event handler for the menu item. In
the menu event handler, I have code which does the following:

void on_about_cb(GtkMenuItem *menuitem, gpointer data)
{
        GtkWidget *mainwindow;
        GtkWidget *w;
        w = GTK_WIDGET(menuitem);
        do {
                g_print("Widget ID is %s\n", gtk_widget_get_name(GTK_WIDGET(w)));
                w = gtk_widget_get_parent(w);
        } while (w != NULL);
}

The sequence printed out is

about
help_menu
GtkWindow

Somehow, the menu bar itself, the vbox and the main window are not in
the hierarchy.

I wrote this test because a call to gtk_widget_get_toplevel returned a
window that was *not* the top level window into which the vbox is
added.

Am I doing something wrong? Is this a glade bug? I noticed this in
programs which use glade code-generation as well as libglade. Or could
it be because the popup menu is a top-level window in it's own right?
I need a pointer to the parent window to which this menu belongs,
since the window has a structure with information, added using
g_object_set_data. Is there some other way to do this?

Thanks

-Jim