After years of wading through people with GPU problems masquerading as CPU problems, it really does look like you've got the holy grail; a true case where something legitimately weird is happening. I'm afraid I don't have a good guess as to what's going on there though Andy.Korth. You are the chosen one. One idea: According to the profiler you don't have anything opaque being rendered. Is there be anything opaque in your scene? If so, it certainly looks like Opaque is on, but maybe try clicking the little green button next to Opaque under GPU Usage and clicking it a second time to turn it off and on again, just in case.