Hello I don't know if you are still having the problem with streaks on your renders. I too had black streaks on my renders mostly when I raytraced, Here is how I seem to have solved it. If you have been working with your scene for awile to get it just right by making a lot of test renders first. When you are all set up for a final render Just before you push your render button to start your final high quality render. Reload the textures, its at the top under render controls. It will take a minute for poser to reload all the textures. Than push render. This seems to have solved this perplexing problem for me. I tried many other things and found this by accident and it seems to work. Hope it helped