That's apparently a known bug with V4 and External Morphtargets ON. I'm afraid your old scenes are hosed, but any new ones you save, with User External Morphtargets UNchecked.. should open.

Do they?

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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.