My brother is unable to log-in to the forums!

He is logged in to the site. When he clicks on the "Forums" button on the sites masthead the page refreshes and takes to him to the forums but logs him out.

If he tries to log-in ---> he gets the error message that this user name is alreadty logged in!

Of course; he can't get here to ask this question himself!

Does anybody know how to fix this???