Doncha just love weirdness? The only other thing I can think of is something going on with how the shadows on the intel calculate. I'd try turning off soft shadows if you have them enabled, and see if that does anything. 

Otherwise, you win the prize this week for "What the heck is going on here?" :-/   Tell the company that they need to spring for C6. :D

I'd be happy to take a look at file if you want. Contact me via site mail if you want to.