Error -4994 - It's bugging me

[William Wallet]

I'm sorta certain that I have to open port 3453 or something, or maybe I don't.
Actually I know nothing. The long and the short of it is that Cid and I used to be able to host and join each others games, but since around the time we updated to 1.5.1 or so, it's been giving us firewall errors (-4994).

Is this something silly? We've got absolutely no frickin' clue. (We can still join other people's games though, like when the Myth Jumpers play).