OK, My son has Just run a trial, Downloaded 11. 8.800.94, uninstalled previous flash verson and installed that. Poser still had no libraries. He then unisntalled Adobe Air, and Poser is now working properly again

 

So it would appear to be something to do with the latest Flash and Adobe Air updates.

The greatest part of wisdom is learning to develop  the ineffable genius of extracting the "neither here nor there" out of any situation...."