It should be fairely easy to reproduce though I'm not sure what other factors cause it.

An AI had two planets with artifacts on them. I wanted them. As TEC Rebels, I hired pirates to raid those two planets respectively where I had stuck my Akkan Battlecruiser in preparation to colonise the planet once the pirates had bombed the living daylights out of it. Keep in mind at this time I had reseached the upgrade to make my allies with the Rebel and Pirate factions.

 Anyways, I got the planets but now the AI just sits at this black hole with a huge fleet that he had prior to my crafty takeover of his planets and every 2 minutes or so tells me to defend one of the two planets I now occupy that have pirates around it since they were not all killed. I think the problem is that the AI thinks that he still controls the planet or perhaps the AI coding when it comes to recognising that I'm an ally with the pirates is buggy?I don't know. What I do know is that now all he sits around at the wormhole, refusing any and all mission I offer him, and outright doing nothing.

 I have tried chainging his difficulty from Hard to Normal back to Hard, then to the difficulty above that (don't remember what it's called) still nothing.

If there's already a topic on this I'll take this one down pronto and with my appologies. I didn't see it when I did a search. Though it may be titled a number of different things.

Anyways, great game so far even if it still doesn't run the greatest on larger scales. Love the new graphics BTW.