Being attack while in Peace

[sealtx72]

I am playing as Spain, I was at peace with all AI Players, then The Roman empire attacked me, I was able to defend myself and captured one of their cities. We briefly had peace and there was a Military Emergency because I captured a city. Immediately I went back to war with Rome and no other player join Rome. So I started my campaign to bomb as much as I could, but every time I try bombing an area where there is an AI Missile Cruiser nearby that I am not at war with, they inflict serious damage on my bomber. I do even see the message that that other AI that I am not at war with, damages my stealth bomber. Is this a bug?