Well, I think Catlin has it pegged, it must be a bug. I reduced the ranged falloff to 1 and it still colored the spots. Eliminating "light sensitive" caused all sorts of ugly problems. I guess I'll have to render the scene in a couple of passes... Another thing I've found a problem with, additive light. Without checking additive, the volumetric light just doesn't work, but when checked, at first glance, it looks right. unfortunately, it is not so. When looking through the visible beam of the spotlight, the background that is perpendicular to the stream of light is illuminated, which, of course, cannot happen... light has a certain amount of coherency. Gah! I think I'll go back to simple room interiors, maybe NVIATHAS (naked vikki in a temple holding a sword)!