Just downloaded and installed the enhanced edition, however when I try to start a single player game, the game says "connection failed" and exits to the title screen.

Naturally I blocked the game from connecting to the internet in my firewall, because this is GOG and it doesn't have DRM, and I never got this in the original edition of the game.

Have larian tried to force some online check, or does the game think it's a multiplayer game over the internet?

Help!!

I also noticed a "Steam_api64.dll" file in the "shipping" folder. Have larian mixed up the versions?

Exact same problem here.

Already checked this out. Ain't worked.
Only way to run game - allow it to use internet connection.
I wonder what it needed for while singleplay? And why it isn't listed in requirements section?

Yes, this is true. I've discovered the game works fine if I remove my network cable. It doesn't need internet access, but the firewall needs to allow it "access" to create the lobby.

Didn't do it for the original game, though, which was why it surprised me. Also, I think Larian could put a patch out where this could be disabled in the options for those, like me, who were initially paranoid.