Cage, before we carried away with a multitude of suggestions, let me point out one important thing.  I quickly skimmed through the posts, so I may have missed a thing or two.  If you are using any of the Pro series versions, enable render GC to 2.2 for all material shaders dependent on GC nodes.  Chances are you could be doubling gamma if both shaders and render settings are equal.  So your either render with GC enabled and set every GC shader to 1, or use CG enabled shaders and set render settings to 1.