I assume that you have poser 5 and you have just applied the service release 4.1. If this is the case then follow these steps. Run Poser. Go to the material room and select the background colour. You will notice that there are a few rogue nodes with the name background. Delete any that are not connected. Go back to the pose room and set poser prefs to launch from prefered state. Note. You will need to repeast this process for any projects you have saved since service pack 4.1.