whenever there is a firewall [software or hardware] or a software [such as anti-virus] that would be closing some ports without even notifying you.

I still remember my friend, could not play World OF Warcraft [Online Game] because his D-Link was blocking some ports. We did a port forwarding and it worked like a charm, later he face it again ... It won't even open the game.

The last thing he did was installing Symantec Security Solution on his PC, he could not believe it. I told him, uninstall it and you will see and it did work. Symantec was doing a great job, blocking the game from even running without even saying eheemm ... I'm blocking this are you sure that you got no trouble so far?

Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment. (Gautama Buddha)