If the server was truly in the DMZ, then your problem is related to the IP address you're using in your config files. My guess is you are probably using your local address scheme, like 192.168.x.x in your configuration but when the server tells a client over the Internet or on another network that this is the server IP, the client tries to hit that address which is either non-existant or on his/her own network. You must put a public IP in your configuration file. Easiest way to get your IP address by visiting
www.whatsmyip.org.