I've been trying to play Sacrifice using GameRanger with a friend of mine. We both got Sacrifice from GOG.com.

While either of us can host just fine, the other gets booted out as soon as they try to join the lobby, given the message "CD Key is in use".

Anyone have any idea what causes this or how to fix it?

Thanks!

I think you need to request a key from GOG support. My understanding is that the default installation uses the same key for everyone to simplify their distribution mechanism.

Ah, okay that makes sense. I'll see if I can find an new one. Any ideas on how to change the CD key that corresponds with the game?

You should be able to do that through Options then Miscellaneous from the main menu.