That's what I suspected, but nothing happened. So I tried again (and I have to write down Numpad5 somewhere, just in case).
Note: This happens with the outdated 1.0.2 version, it might not be an issue in 1.0.3 anymore. I still have to install that one
It's just strange that one day it worked and the next one it didn't without me changing anything.
This is the log shown in the command line window during startup.
edit: Yeah, seems to be good in version 1.0.3, tomorrow I'll check if it still works
Btw, I got the textures working the same way it was described earlier.