[xwiki-users] Authentication error

Happy new year! I recently came across this strange behaviour. We are 20 users on our XWiki, we have identical rights on the wiki, we authenticate via AD/LDAP. Now 4 users get an error at the main URL /xwiki/bin/view/Main/ telling them they do not have access to the page. When I look at the user rights for Main they have the same rights as everyone else and should be able to view it. When the same users go to /xwiki/bin/view/Dashboard/ they can view that just fine (it's the same content just a different view, right?) Has anyone seen this behaviour before? Is there a simple fix, am I missing something? -- Regards/Mvh Daniel Lundh