Maybe his game is freezing, and it's not a problem of IP
Alterego, when you host a game and start it via gameraner, your game is automatically launched by gameranger and you should arrive on the AOM page, where you see the other players, where you can select the gametype, map, your team...
and at the top left corner, there is you IP which is displayed (this IP must be the public one, that your can see on www.whatsmyip.org).
If your game freeze after entering your name and before hosting the DirectIP game, it may be normal if the freeze doesn't exceed 1 minute, just way for a while...
If freeze doesn't stop, try to launch AOMX manually, then mutiplayer, LAN and host a game (don't check IP by this way just it will be wrong). Check if the freeze continue when you launch it manually.
Do you have tweaked your game? have inserted overrideaddress or +Directipconnectivity or something else anywhere?
Do you have any antivirus or firewall that could block your game?
Is your game up to date with 1.03 crack? http://sites.google.com/site/aomfreeonline/downloads
I think you should try to uninstall AOM and gameranger, delete all the folders linked to these softwares and try a clean reinstall.
Is the problem the same for AOM.EXE? and have you ever played on eso with AOM(x)?
The best defence is attack!