yyahoo: And, of course, our shelf views/files are the same (save the fact that I don't have the Downloader turned on), even though we purchased the game/DLCs differently.
What happens if you try to download the file without using the GOG Downloader?
yogsloth: You're not going to believe this.
I was able to download the file directly, without using the Downloader, as you suggest. So I grab the full file, go to install it.... AND...
You need to download the whole lot and re-install. I have just been over this with the Democracy 3 Drones & Clones DLC.
The new GOG version is incompatible with the older version, so you have to reinstall with a more up to date version. The current version up and running should work. It did for me when I reinstalled all of the SotS yesterday, and then Democracy 3 today.