I've played a few 1v1 and small FFA games against easy AIs and am now engaged in a 3 star, 8 opponent match against normal AIs.  I started out as the TEC in the middle star system with 2 Vasari opponents.  Another star system has another Vasari opponent.  And the third star system contains three Advent and one TEC opponent.  I was instantly at war with my closest Vasari neighbor and I did my best to please the races outside of my star system.

Long story short, I eventually made peace with my Vasari neighbor and ganged up on the other one.  I took his worlds and then turned my attention to the Vasari who was the lone force in his own star system.  He was claiming worlds in our system so I took those.  And then, much to the delight of the other AIs, I backstabbed my former-enemy-turned-friend-back-to-enemy Vasari neighbor.  Over the course of all of this I had made peace with all three Advent opponents.  I was at 100%, 100%, and 83%.  The TEC and had got into little scraps that kept us from being friendly.

Then, all of the sudden, two Advent buddies of mine declared war on me (one 100% and the 83%) and our diplomacy dropped to 0%.  They dropped all alliances.  They both offered me missions soon after and I gave one of them 4000 metal (as the mission requested).  All of the sudden they were back at 100% (but without the Cease Fire and Peace niceties).

What happened?  Did the AI realize that I am becoming the big dog and turn on me?  Or did my heavy use of my two Novaliths in the extermination of my neighboring Vasari have something to do with it?  I haven't read anything like this happening against computer opponents.  I mean, I'll roll up the sleeves and kick their psychic butts now, but I was just curious.