rworrilow,
If you added several runtimes into the library, then moved them when Poser 6 isn't running, the  next time Poser6 starts, it will look for those runtimes and it may take a while, so seems like it is hanging. 

All,
As for QT update installation, yes, I also had that smash-up experience for my Poser 6, and I had to uninstall the QT (or I think I rolled-back to previous version).  It was easy to link the QT update to my Poser6 crash because it was the only change to my computer, and it affected my Poser 6 launch right afterward.
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Eternal Hobbyist