Maurice,
To clarify, are you trying to invoke a callback or a postback on menu click?
Am I right in assuming that you want to refresh a portion of your page (within the CallbackPanel) when the user selects a menu item? If so, please note that the menu itself does not need to be in within the CallbackPanel.
In any case, please browse to:
http://www2.syncfusion.com/2.0/samples.aspxThere browse to the Tools.Web/CallbackControls/ProductMenus sample. There is some code there that shows how to invoke a callback on a CallbackPanel on menu click.
Regards,
Praveen