The short sweet answer is that face normals determine which is the back and which is the front side of any given polygon. Normals can affect things like how reflections and refractions are calculated which I think is the problem in your case.

You can toggle their display through the Display>Polygons>Face Normals. Or a quick and dirty way of checking by a glance is to turn off "Two sided lighting" under your panel "Lighting" menu, there will be a color difference between the front and back sides. You can change the normal direction of the offending objects or components by selecting them and going to Normals>Reverse.

More on normals>>