unfortunately I can confirm this strange behavior in Poser 7 SR1 (never happened in any other Poser version before). There must be at least one non hidden figure in the scene. Otherwise Firefly renders a blank scene on my machine. And to make things worse, this figure must be a people figure (V3, V4, A3, etc.). I have tried it with many different props and with other "figures" like buildings, vehicles, plants as well. No way! Really strange and I have no clue why this happens.