Are you using Poser 5 by any chance? And with some files in another Runtime? I've had that error once, but that was after I had moved some files around (found out the hard way that you shouldn't) Make sure that the !Daz folder is in place. It needs to be in RuntimeLibraries and nowhere else.

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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.