Did you flatten the cube? Try using the one sided square instead, that sometimes helps with these artifacts. I am not 100% sure why it happens, I had it happen recently with the Daz freebie temple as well... You're using P6, right?

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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.