I can't render anything past about 48 samples, either.  And when I try to run the GPU (which Poser apparently recognizes), Poser complains about the lack of a GPU kernal. I have an older NVidia GTX 650 Ti, which may or may not be part of the problem.  (Going now to run and older version of Poser to see how the GPU fares.  Given that I don't use the GPU, I suspect it doesn't work for me and I simply forgot.)

Speaking of that, does anyone know if it is possible to run more that one version of Poser at the same time another version is running? It's sometimes useful to run an older version when a newer version won't run a script, as one example.