P4 1.4ghz - 384ddrram - GeForce4ti4200 - Winme (was using Myth II v1.4.3)
Just letting you guys know that after the 1.5b1 installer has done its duty, launching the game from the installer will work ok until you click the "preferences" option in the main Myth2 screen. This will crash the game to desktop. I also noticed that 2 options in that screen were not selectable (saved games/saved films).
After I relaunched the game everything seemed to work fine (all options were now selectable in the main screen). I did not need to change any options (preferences) nor did I need to re-enter my username and password to connect to a server.