[couslee]

well, the game shows you to be incorrect on that. One of my angry planets just went rioting. I did have 10 police troops on the planet, and 1 combat ship sentried in orbit. there are also 2 colony ships, but they just arrived the previous turn and are only passing through. Based on what your saying, the happiness factor should not be heading in a negative direction.
(The surrendered race in question is the Bobroba States if any is curious).
The only thing I can think of that would send this planet in a negative direction is my trade treaty with another race. Since the race description states "warriors" I am assuming they are bloodthirsty.