Wow, lots of developments here. I was planning to report all the issues we've been having in the DBB bug report thread, but was quite busy for the last few days. Appreciate you helping out with this.
Where does the d2x.log file get placed? I tried adding -printlog to my d2x.ini but can't find this file anywhere. I am using the data directory system, if that makes any difference.
I think most of the problems with the games being completely invisible are related to the host's firewall port forwarding settings. I have always been able to fix that problem for my own games by messing with those options.
The stability is still an issue for me in the latest version. I am basically getting an instant crash to the desktop and the generic windows error message when I start a multiplayer games in certain maps. Strangely, this only happens with some maps (I get the crash with D2 Counterstrike and the official Dogfight pack, but not your custom Dogfight map). However, even if it doesn't crash right away, it still crashes on both computers whenever someone else tries to join. The older 1.5.121 version we've been using doesn't have these problems. I tried creating a new pilot, but that doesn't help. Also, I haven't run into any problems in singleplayer.
I'm doing some summer courses that started today, but should have time to play again at most times this week. I could put a game tonight, but it's not going to stay up very long with these crashes.