If it's a NAT problem you probably need to activate Port Forwarding. I'm not sure if opening ports counts for the same thing because for Port Forwarding to work it must be able to communite both ways, i.e. can both send and recieve data. Merely opening a port for listening isn't going to work.
If you meant you've activated Port Forwarding by opening ports then please disregard my blabbering. 😛