Quick update: As I already suspected from the beginning, access rights was the problem. And this is the recipe:
- Open a command prompt window with administrator rights
(press the Windows key, then type CMD and on the found item do a right click and choose ‘Run as Admin’ - Into that Command Prompt window copy and paste the line
icacls C:\ProgramData\Steinberg\Content /grant *S-1-5-32-545:RX /T - and press the Return/Enter button.
What that icacls command does is going recursively through every file below the given path and giving at least read access to every user to every found file/folder.