Indeed it looks like Quicktime messes up Poser and/or the graphic card settings. Today I had same error as Mikesimoni decribes above. Poser 6 just vanishes during startup.

I had Poser 6 running fine for a few months, installed Quicktime yesterday and indeed suddenly Poser vanishes during startup. I too have a (rather old) Dell PC, but with NVIDIA Quadro4 900 XGL.

I uninstalled Quicktime and rebooted (real cold reboot, so really off and on recommended). Poser works as before, but no quicktime.