Automatic Peace Bug?

[Sam_Finch]

A country declared war on me and we were at war for only a few turns. Then a message from them popped up saying they wanted to have open borders. I declined because I wanted to defeat them, but when I got out of the box a message popped up saying we had formed a peace treaty. I thought maybe I pressed a button wrong or missed a pop up so I ignored it. Then I went to war with another country and after only a few turns the same thing happened again. Is this supposed to happen? How am I supposed to defeat countries if they run away after only a few turns?

 

[Guicx]

I've got quite the same problem :

Playing Japan, I declared war on Iroquois and invaded them. After some turns of war, I get the screen on which I see that the Iroquois have denounced me publicly. Closing the diplomatic window, when I get back to the map screen, a peace treaty has been signed between us!
However, I did not receive any offer for peace (and did not accept, a fortiori !).

This bug happened on a custom map, playing vanilla game, DirectX 9 mode; version is 1.0.1.217.