shading flickering on and off

When I move my character around my game level the shading flickers on and off. I have a default settings sun lamp and basic temporary materials (default material with a color selected and specular turned off) which I’m using as “color placeholders” until I am ready to do the uv maps. I thought it might have to do with the distance from the lamp but the shading still flickers right under the lamp as well.

Any ideas of what’s going on here?

EDIT: I figured out the problem. The lamp was only calculating objects of one layer at a time. When layer one objects were shaded, layer two objects weren’t (and vice versa).