[Zubersoft]

That's very interesting. I buffer three pages backward, so that means when you turned four pages, it released the bitmap that was stored for the black page. Hence when you turned back, it was re-rendered properly. What this tells me is that a black image truly was rendered and saved for some reason. Are you currently using the quality render preference setting, or the speed? I just want to double check which PDF render library I should be using.