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.
I have a problem with displaying my sub menu in the main frame.
In the left frame which is called "leftmenu"everything works, the menu is shown.
In the main frame, the submenu says at the first item "undefined". What seems to be the problem?
I'm guessing you have a menu array in your menu_array.js file that does not actually have any items defined. But that's just a guess. Can you post a URL so we can see what's happening and look at the code behind it?