Can't declare war

[Bowrider]

Using Civ IV on a Mac.

I am in a situation where I'm stuck and can't declare war. When I engage diplomatically I'm turned away as the AI won't talk to me. I can't invade its territory either. The game won't let me. And the <opt> command isn't working either.

Any suggestions why this might be happening and what I can do about it?

 

[2metraninja]

You may have a 10-turn cease-fire which is unbreakable.

Either you made a peace after war in less than 10 turns ago, or you received/gave a tribute in less than 10 turns which denies you the possibility to declare war. Wait few turns and try again.

Hope this solves the issue.