MULTIPLAYER: CityStates declaring war on all players

I played a multiplayer Civ game with my buddy this weekend, and we ran into a wierd glitch.

I was going for a domination victory and he decidedly was not. But everytime a new CityState would declare war on me (because an opposing Civ in my war had allied it), it would declare on my buddy, too. He never DoWed anyone, yet peace was blocked for him until I finished up my war.

Has anyone else run into this? Or was this a one-time bug?