Thanks for all your help. Unfortunately I could not fix the problem. I checked windows update, tried to reregister Kernelbase.dll (I got some error on this), I created a new user...
But the workaround is fine. I started the server, join it and found some nice place to start creating a settlement. Fruits, coal, copper all around. I think I will start enjoying the game by using the dedicated server instead of further searching for the bug in my system.
Thanks a lot for helping and for developing such a great game!