Downloaded and installed new version - 1.0.7.4 hotfix, but the game doesn't start.
Launching with the desktop link brings up a message saying something of target program being missing or modified. That's because installed game folder contains no Arcanum.exe.

Could it be that your Antivirus-program automatically blocked it ?

As i just updated my games through GOG Galaxy, Avira Antivir says it has Heur/Agen.1018502, most likely false positive.

Thanks, most likely that's the case. Opened the game folder during installation and saw that exe-file disppearing just a moment after the process. Tried making a backup copy of the exe-file, but that disappeared too.

Just noticed myself, that my avira blocks arcanum.exe during update.

Is GOG doing something fishy with this file?

Same for me. I get a DISK ACCES PROBLEM.