Good races will go to war with each other from time to time without any help, anyway. Just in my last game I, the Iconians, was being beaten up by both the Yor AND the Drengin and what do the Terrans and Torians do? They declare war on each other . Yeesh. Of course, after I beat off both the Yor and the Drengin I quickly allied with the Terrans and Torians after they ended their little spat.
Oops, sorry for the double-post. My browser went a little screwy.
I'm fairly sure that there are a couple of things that will cause an ally to turn against you, although I've only experienced one. If you have a very low espionoge rating with an ally there is a chance you'll get this type of message: "During an ambassadorial dinner, you ambassador accidentally insulted [insert leader's name]'s wife. The [insert civilization's name]s have declared that only war will teach you manners. This could have been avoided if we had more money invested in espionoge."
