Looks to be something set on your server for permission to access.
Could be to double check file folder permissions for the forum as per in the install docs.
We don't know if it is a windows or linux site but it could be something that was set in the htaccess file prompting for a login.
BTW classic versions are not supported anymore.
Moving to classic forum.
Last edited by Ruben; 06/03/2012 1:05 PM.