This is driving me nuts. It seems like when certain MR shaders are assigned to objects and you select the objects while the UV texture editor is open, any objects using that shader turn pitch black. It seems to be a problem with these shaders:

mia_material
mi_car_paint_phen
mi_metallic_paint
misss_fast_shader
misss_fast_skin_maya
misss_fast_simple_maya

All the x and passes versions work fine, whats bothering me are the skin and simple sss shaders. I tried reconnecting the shader to it's materialInfo node only to have the problem pop up again when the scene is reopened wtf!