This is the basic Figure or Pose folder, not a sub-folder? What files (as opposed to folders) do you have in <Poser 6 folder>Runtimelibrariescharacter and <Poser 6 folder>RuntimelibrariesPose? Are there (probably recently added) folders in there with odd characters in the names?

There was a stage at which D|S crashed every time I opened a particular pose folder, and that turned out to be a bad thumbnail, but I would expect that (if it's still an issue) to affect two root library folders.