Can't start the game anymore. After clicking on "start", the follwing two error messages appear:

1. ADOM Error
Can't determine the 'my documents' directory.

2. ADOM Error
Couldn't switch to directory " (3 was called for).

Uninstalling/Installing didn't fix the issue. Starting the application as admin didn't fix the issue. Don't know since when this occurs. I only know, the the game used to start properly a few months ago.

Any suggestions?

I had the exact same issue and the problem was that Windows Defender was blocking access to certain folders. The feature is called 'Controlled Folder Access'. If you go into this you can turn it off or allow an application through the protection (this is what I did).

On windows 10 it should be found at Settings> Update&Security> Windows Security> Virus and Threat Protection> Ransomware Protection> Allow an app through controlled folder access