Why do Portal navigations appear only after navigating to one of the contained components?

I'm developing security for a client (for the first time) and have most of the T's crossed and I's dotted.  However, during testing of my new roles/users, I'm often finding that some portal navigations appear for selection after I've navigated to another related component (e.g. using the navigation "breadcrumbs").  For example, I open the eProcurement folder and only see Buyer Center, Reports & My Profile.  Once I navigate to reports and click on the eProcurement breadcrumb, I see the other components, like Create Requisition & Manage Requisitions.  What causes this and what might I do to fix it?  I've run