I've seen it happen, both in XP and Vista. But a reboot has always solved the problem for me. And I mean a proper reboot, not just shutting down Poser...

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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.