Hi,
You may find the following helpful, or at least a good starting place to figure out the problem you have:
Development: Themes 2.0 adding courses and categories to the custom menu
Another useful totorial may also be of use to you too:
Development: Themes 2.0 extending the custom menu
also
Development: Themes 2.0 overriding a renderer
More tutorials can be found @ Development: Themes 2.0
Mary