problem with custom menu

[John Taber <jtaber johntaber net>]

I'm having a problem with the newer way to use a custom menu - can someone 
help out - thanks.

fileMenu = new Gtk::Menu();
openMenuItem = new Gtk::MenuItem("Open");
fileMenu->attach(*openMenuItem,0,0,0,0);
fileMenuItem = new Gtk::MenuItem("File", fileMenu);
menubar = new Gtk::MenuBar();
menubar->append(*fileMenuItem);
mainBox.pack_start(*menubar, Gtk::PACK_SHRINK);

: Gtk-CRITICAL **: file gtkmenu.c: line 3836 (gtk_menu_attach): assertion 
`left_attach < right_attach' failed