Frozen leader changes side during a war? War declaration after bugged research offer

[ThorRex]

In this 1700 game as Ramses, I was at war with Genghis and bought Napoleon onto my side. A few turns later, Nap appeared to ask me for a Research Agreement. I was unable to accept and got a continuing spinning globe. Finally, I tried an "escape key" and was able to leave the screen. Nap and two other AIs declared war on me!

 

[dshirk]

I cannot seem to reproduce this problem from the attached save. Is there a specific sequence of events you go through to have it reproduce?