Poser 7 does also seem to be fairly temperamental.   I have had something like this happen:  three characters in a scene, probably rather too many lights and raytracing on in the manual settings (and set to 6 or 7, maybe).   Poser seemed to go through the render preliminaries happily enough and then stopped, just when the actual rendering seemed to be about to start.   I know that the render had stopped completely, because Poser wasn't using any CPU.   When I tried to re-display the preview, I got that old texture-size problem and Poser promptly shut down.   I re-started and was able to render the whole scene with exactly the same settings.  

I had previously tried to do a quick render of the same scene, possibly with a couple fewer lights and with very unambitious render settings - that brought Poser down in seconds.