Hi,
I don't know if you came right with this, but I'll answer it anyway:
Any user that is higher than a Registered user (Author->Publisher) is seen a a special user. This means that is you assign a module/content item/menu item special rights only the higher up users can see these items.
I also wrote a small component that can be found at
Shadowrain Design which allows you to give rights to specific users to see specific menu items only. (It's not for content or modules)
Hope this helps.
Regards
Kbman