If any of you have come across a problem in SharePoint 2003 whereby some users are not able to see a link to an area within the main portal page, the solution couldn't be even easier. Ensure all users required to access the area are setup with access rights for that area. I always thought that even if a user does not have access to an area the link will always be shown in the navigation within the main portal site. Obviously I was wrong. Silly me!