This should be fixed now, you can download the updated MissionLauncher.zip here:
https://forum.dune2k.com/topic/26661-dune-2000-106p-game-patching-bug-fixes-new-features/
I have a fix for it somewhere (Had the same issue on a different program before).
Will have a look, but you need to have some patience, not sure when I'm updating the mission launcher again