Sometime when i do a radiosity render the faces of some objects ‘streak’ the base colour. The objects are generaly modeled with curves and converted to meshes.
an image: http://dittohead.blender.tripod.com/images/streaking.html
My best guess is that the streaking is caused by the light calculations of the “caustics” for lack of a better word. I say caustics because all of the light in a scene is taken into account in a radiosity render. The light off of the black mesh objects may be added to the color of the blue face. I have no solution for this.