I think I'm encountering a bug that's very frustrating. I cannot attack Montezuma and he's spreading like wild fire. When I look in the Diplomacy window it says that our relations are "hostile". When I look into the list of current deals it shows none. When I look into the list of past deals it shows that at turn 209 we had a 10 turn peace deal but it's now turn 240 and I can't attack him.

When I try to use missile units to attack him they simple cannot target his units. I cannot move into his territory and if I engage him in diplomacy the "Declare War" button is disabled!

I even saved and restarted just to see if it was a random glitch but I still cannot attack him. What's the deal? Is there some hidden screen I'm not seeing that I can use to see how much longer until I can attack??