Please note that official support for this menu version has now ceased. There are still plenty of users, though, and the forum is still running. Some of our long-time users may be able to help you out.
On items that simply have a sub menu and no link associated with them, NS4.x has some major issues. It works fine if you click on the text or image in the menu item, but if you click in the empty area, the page tries to go to a show-menu page. For example, go to Andy's homepage, on the left navigation, go to any of the menu items that have asub menu, but do not link to any pages (Complex, Forms, Live Samples, etc.) try clicking on the text, and everything is fine, try clicking to the right of the text (where you pointer is once again an arrow) and it goes to a page that doesn't exist.