My 'Guess' is then that the router at the ISP is the issue. You have no control over that. You could try asking them to open port 6346. There may not be too many options when they have control over the device (most high speed modems/routers have internal NAT firewalls.) It sounds like it doesn't support UPnP or else the distance between means your computer has no control over it which sounds more likely. You might try changing connection ports to one between 49152 - 65535 but same issue most likely. Another few ports to try are port 80, 443, 427, 1111. To change connection port, go to LW's prefs & choose Advanced -> Firewalls. Change both connection & listening ports. Or at least listening port. Turn your OSX firewall off temporarily over this time. If it works then set a OSX firewall rule for that port & then turn it back on.