Global Illumination - Dark Shadows

I am getting these dark shadows on some of my geometry with global illumination. I'm using real-time precomputed only. Has anyone else experienced these? In this case it's above and below a floor. But it's not happening everywhere. And I cant find any problems with my mesh or UV's either. I'm using the default settings, just un-checked Baked-GI. Thanks.

 

The problem was my geometry. My mesh data originates in Autodesk's building design package, Revit. The short of it is, anywhere to normal faces touch, or if there is a large area of poly hidden from the light, like a wall above a ceiling, you rish these shadow. By removing the red polygons in the first image, I was able to get the results in the second and third.