In a situation like this I make sure all users can see the page and the module, then I give edit rights to the Registered Users on the module. This allows everyone to see the forums and then only registered users can post. (This module does not support users who are not logged in posting anyways). If you then want to further restrict permissions you need to do it from edit forum level. ONLY set authorized edit roles on an individual forum if you want to restrict posting access further than what is set at the module level. Then, if you want to restrict who can see further you need to set the authorized view (and check private forums for both of these changes as well.)