Well it sounds as if the problem is the router. A router has what is called an NAT firewall in it. This firewall prevents all incomming connections unless you specifically allow it. What it looks like is, it is blocking the DCC request from being acknowledged. To fix this you need to change port forwarding settings, if you forgot the l/p to the router, there is usually a little "reset" button on the back that can reset it to the original password (which can be found in the manual). If you can't do that, then I can't really help you...
