So I'm using Mental Ray to render, along with caustics, global illumination, etc.

I keep having trouble with my "mi_car_paint_phen" textures and I can't pinpoint what's causing the problem. One minute they're looking good, then I'll make some changes and suddently it's super flat, using only the base color and ditching the "lit_color" and prettymuch all of it's detail.

Is this something that any of you have run into?

Is there a setting or node that I need to be paying attention to?