It seems like the infamous burned highlights problem which occurs when you are lighting with IBL and normal lights.
When you are using the already mentioned Advanced MIA material you have to activate "Clamp Maximum for HDR rendering" at the bottom of the Optimization Tab and set to something reasonable like 1.2 or so. So the highlights are clamped and don't burn out. Another option is to tweak the "Highlight vs Reflection Balance" on the Additional Options Tab and set it to a very low value like 0.1 or less. Generally it's a good idea to deactive the specular contribution off the lights if your lighting with IBL. Cheers, Stephan.
