My girlfriend and I bought NWN Diamond edition to play together... unfortunately, we are having problems seeing one another through the Multiplayer. Despite both being logged on, we register as Offline to each other. Initially we were able to Direct Connect into a game with each other, but it was interrupted by real life issues, and when we tried to go back later that day, it wouldn't let us. We can each log into certain other worlds, which makes me think that it isn't a router or firewall issue (she has disabled her firewalls to try). We are both behind wireless routers, however, and I can't for the life of me figure out how to open the massive number of ports in Windows Firewall (which only seems to open one port at a time).
Even though we can both see other games and log in to them, I don't think that we are seeing the same games, and we'd much rather just create a game for ourselves rather than use another world.
If it makes any difference, I'm using Vista 64 bit edition, and she's using Windows XP.