Playing the Terrans, Mars population refuses to grow. It's approval rating has varied, of course, but for the bulk of my game (Huge galaxy, Tough setting) its population hit 2.5B and froze. The ceiling with the improvements I put on it is 16B.
I also built a Fertility Clinic and Food Distribution center on it with no results. Like all my planets I have at least one Farm and one Entertainment building present.
I haven't noted the problem with any other planet (but haven't canvassed them looking for the problem, either)
I have a saved game if that's helpful. Otherwise, maybe its part of the planet quality bug or somethin'