Does the render stop? The only times I've seen those lines are when I try to scroll in the new window while Poser is rendering. Usually nothing happens, untill the rendering is done but sometimes I can create something that looks like this. However the rendering doesn't stop, and it finishes the pic just fine, so if yours actually stops it's gotta be something else :o)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.