It's one of these things that seems to sometimes just happen at random. I've had it too and it's highly annoying, more so if you can't remember the trick to fix it (as I couldn't last time) I don't think it's caused by a script. But on the other hand I don't know WHAT causes it either, so... who knows?

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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.