I run an Actiontec HD701D modem with NAT to an Airport extreme base station to laptop etc. As you might expect I get double NAT issues.
I tried a lot of different things to forward a port, but no luck.
Currently the airport is in bridge mode letting the modem handle the NAT, but still can't forward the port.
Also to note: firewall is off on the router, firewall is set to allow the application in OSX 10.6.3 and I did forward the port in the router. No luck.