When you choose an initial dispersion greater than zero, you run the risk of having one of your units placed right next to a unit of another nation. When that happens, you are at war and cannot make peace - "Diplomacy - Meet" is clickable but it produces no diplomacy screen. So you are perpetually at war with that nation (until one or other of you is eliminated).
I hope someone can fix this bug. To see it in action, choose a small map and large number of nations and maximum dispersion (10).