I was negotiating a peace treaty. Requested the peace treaty and then a planet. The second I click on the planet it Crashed to desktop.

I reload, start again and select a planet first, a different planet, then I selected the peace treaty. Again with the crashing.

It was a minor race the Jagged Knife race form a mega event (I think). Any other combination seems fine, planets and peace treaties crash every time.

Granted, there is no other race presently at war with me to test it with other civs.

I will say that I've modded the game a bit. I've changed the hit points and such of all the hulls and the cost, size, and sizemod of all the weapons. As well as removing the rangeability from all life support techs. I wouldn't have thought any of that would effect the diplomacy screen though.