Why Did This Cheesecake Catch on Fire?
I know it sounds like a stupid question, but are you sure the oven wasn't in "broil" or "clean" mode? It seems unlikely that a regular shape of flammable would emerge from a fairly homogeneous mixture. It seems more likely that a heat source in the shape of the burn marks on the top of the cheesecake was radiating directly onto it. It could have been an intermittent malfunction with the oven, too.

Other than that, I'm lost. It's quite a mystery you have on your hands there.