That still shouldn't CRASH mental ray. It should be slow, as it's writing to the disk (virtual memory); but it should still render. Idk but that fixed it for single-frame rendering the moment I've reduced polys on spheres and other objects (the moons had the most polys though because they had irregular shape and such). Then I forgot the Allocate on Heap option on, and the batch renderer began to silently crash. Good thing I'm out of the woods now.