Kerbal Space Program

Upon more experimenting, the above behavior happens with with terrain detail set to medium. With terrain detail set to low, the problem is exacerbated, with the 'dark zones' being much larger. Though on the converse, areas that actually register lighting effects are much brighter.
On high terrain detail there are little to no 'dark zones' though, and while there is a slight variation in the brightness of lighting on the terrain, it's not extremely noticeable.

The following screenshots were taken at the same location. (last two were a few meters away from the first.. rolled downhill some before I could get the brakes back on) The first is at low terrain detail, the second set at default, and the last at high.

My guess as to what's happening, is that on the various terrain detail levels, the height map of the terrain is different from the actual terrain. So in the 'dark zones' the game actually thinks the light sources are below the actual terrain, thus don't get rendered.

This last screenshot was taken on low detail in one of the 'bright' patches, and IMHO, is probably how the overkill 4x spots on this rover should actually look everywhere on the Mun surface.

The images I linked orginally are hosted at my house and i'm apparently having DNS issues. if I can't get it fixed in the next few days, i'll rehost images on imgur or something and relink them.. This report is kind of useless without them.