I just restarted the game and it looked like steam was installing another mini-update? But the Version-Number did’t change.
Anyway, i get an error while loading any savegame that i made after the 0.4.0.20 update. Loading an save from 0.4.0.18 is possible.
So I loaded my newest 0.4.0.18 save and created a new one. This new 0.4.0.20 save (post-mini-update?) can also be loaded without error. Strange.