So, I just did the same thing that you did.  I was moving Files around in a runtime and the mouse took the click as a double click and opened Poser.  I closed Poser and continued to move files around.  Now whenever I open Poser I get a message much like yours.  you have to edit the LibraryPrefs.xml and delete the runtime that is causing the issue.  If you have Poser open and click on the remove library option it will list all the attached runtimes.  There are a couple you cannot remove and they are grayed out.  Also it appears the one that is the cause of the error message is also grayed out.  That makes it kind of easy to find.  The long term fix is something i am now working on as it appears to be a windows file time issue as Poser cannot find the time of the folder so that is the root cause..

I will be doing some more tests but at least you have an idea of where the problem is. 

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13