D'oh! In placing the Main Camera I watched it with the Aux Camera and was pretty sure that I didn't place it inside a building. I checked again, and it didn't look like it, but I made all of the surrounding buildings in the set (other than the one that forms the background of the scene) invisible, and now the render is not of a blank area - so thank you! I never would have guessed that one, but now it is part of my ever-growing Poser knowledge (I'm finding this software has quite a learning curve).

However, if I can trouble you again, the render is still not quite correct. In the Preview window, my character is centred in the screen.. In the render, you can kind of make part of her out on the far right, there. Is there an explanation for this? In "Preview Dimensions", I set Width 600 and Height 300. In "Render Dimensions" I had clicked "Match Preview Window". Is there a similarly simple reason for this new disparity that I'm missing again?