Sorry to gravedig, and I'm sure this is an insanely silly idea, but did you reinstall OP at some point and forget the directory servers update patch?
I reinstalled..twice. And, no, I didn't forget the patch.
This problem suddenly went away even after a time, got on, played one lousy day on the Forge. Then, a few days later, tried to log on again, and that damned firewall message was back and hasn't gone away...