Please upgrade here. These earlier versions are no longer being updated and have security issues.
HackerOne users: Testing against this community violates our program's Terms of Service and will result in your bounty being denied.
Sudden fatal error
I have not tried to upgrade to a newer version. Suddenly the forum started to spit out this error message:
Fatal error: require_once() [function.require]: Failed opening required '/home/foobar/public_html/forum/applications/controllers/class.controller.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/foobar/public_html/forum/library/core/class.dispatcher.php on line 529