I believe its now been resolved, let me know if you still have issues!
Technical Reason why this happened:
The newest version of the forum software introduced some extra security features, one of which checks for your current session time (login period) to prevent certain kinds of attacks.
This checking code was missing from the theme code that displays the forum software, so whenever you logged in, you would always have a "timed out" session, as the check was missing.
This checking code was added which should resolve this problem.