I have an issue with volume scattering in cycles. I modeled and textured a model in Blender Render engine and moved it to the Cycles Render engine for render, I ran into a problem with volume scattering. The final render with this option becomes impenetrable dark.
My model in cycles has default material (diffuse bsdf) For lightning source I use a spot lamp (not sun or hemi)
64 bit 8 RAM
AMD Radeon R7 200 Series