wolve666: redownloaded all files with gogdownloader, same problem: integrity check failed setup_witcher3_en_goty_2.0.0.51-1.bin.
I redownloaded that file manually and now the installer and the game both work.
Some files might be corrupt also due to heavy load on GOG servers.
Also tested Polish language pack - works, no issues.
Haldi4803: i tried to install the German Language patch.
Got an error message.... seems like there is no integrity check for Language patches :(
Anyone having the same Problem?
I only tried Polish lang. pack, but that works.
Anyway there are two variants: Either the files are just uploaded by GOG corrupt and they'd need to re-upload them (That's what happened with game files.)
Or this is caused by heavy load on servers - in that case redownloading might help. Try both with and without GOG downloader ;-)