No luck.  I renamed the file, then tested opening Poser.  The same error resulted.  I deleted the new file and also renamed the other two library files in Poser's AppData folder, but still the same error message.

Then I tried opening numerous files in Poser, using the double-click approach, assuming that Windows was keeping a list of most-recently used files somewhere, and I might be able to fill up that list with new entries.  That did not help, and the error was thrown every time one of the files was opened.

Then I searched the registry, using Regedit, for Libraries/Pose.  All I found were two listings belonging to Poser File Editor.

Then I searched for all files modified during the period that this has been happening, and starting a few days before the error.  There were no files listed that were unrecognizable, no data files of any kind that might store a path like this.

Somehow, somewhere, either Poser or Windows must be keeping some kind of record of opened files, to be able to throw this error.  I have no idea where that might be.  My next test will involve replacing standard Poser installation files from backup, but I don't expect that to help.  That old library involves complications with Flash and (Tarim help us all) Internet Explorer, so who the heck knows what could be happening out there.

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.