It could be your ISP...This is a quote from a Sticky within the forum...
6.
Cox is known to filter p2p. Apparently they don't apply it to all people within any area, but more-so individuals. See:
Problem with Cox Communications? ______ Hidden selective p2p upload blocking!. Sneaky monopolistic tactics
Cox Cable bought the local CableAmerica.
New reports on Cox & petition:
Cox Internet - Blocking Ports Petition (<- please sign this petition.)
Broadband reports & also
eMule forums
But it could be your new modem/router as many of them have Nat Firewalls within, so you will need to open up a port .....
So if you have a look underneath your modem/router you will see the make and model number for it, if you can post these details I will get the instructions for port forwarding for you....