I haven't installed SR3 yet (and I'm not in a great hurry to do so), but, I had a problem like yours when I first installed Poser 6, when it had just been launched.   I still had Poser 5 installed and I could render a scene in P5 Firefly, even though I couldn't render it in P6.   I had followed the instructions and looked for driver updates, but I hadn't found any.   Finally, however, I did locate a driver update that fixed the problem.   Re-installing Windows does sound a bit drastic.