I don't see how the Sam Wars mod could be affecting hosted game visibility. All the mod does is change graphics and stats. It doesn't change any system files, and it doesn't change the main executable which is what contains the network code. At worst, people can't join your hosted game due to a stat conflict or missing map.

Quite often many players cannot see mtw/vi hosted games until they relog. That is they have to relog after the game has been hosted, and then they can see it. That's a known problem in mtw/vi.

Another issue is that mtw/vi multiplayer doesn't work with some of the new video cards. Eventually, new hardware will completely kill mtw/vi multiplayer.

You could also get software conflicts as well that prevent mtw/vi from working properly. I'm unclear about how much time elapsed between the last successful hosting of an mtw/vi battle and the installation of beta 8. If any other programs were installed between those two times, it could cause problems.

Warman's computer can't run the installer which is a Visual Basic program. It's possible his Visual Basic run time library is out of date. In any case, Tosa made the zip install which can be used to bypass the Visual Basic installer, and that should work for him.