To my understanding, Windows 8.1 introduces a fatal conflict with a Flash-related dll.

Flash is used in Poser 8 / Poser Pro 2010 and up, for handling the Library in internal mode.

The issue can be resolved in various ways:

 - for Poser 10 / Pro 2014 SM released a SR to repair the issue
 - for Pro 2010 / 2012 the ini file can be altered manually to force the Library into external mode, and to use Adobe Air instead (requires Air to be installed)
 - for Poser 8 and 9 there is no solution, although I think there was a thread referring to the specific dll, and to the way replacing it with a conflict-free version

Next to this, Poser 8 and earlier face issues on Win 7 and up (or even Vista) related to Runtimes / content being installed in the Program Files environment, due to the protection scheme that prevents (user) data to be mixed with program files, known as UAC (User Acces Control).
Some resolve this by running Win-XP, others disable UAC, Poser 9 and up have improved external Library handling.
Unfortunately, older product installers require Runtime subfolders in a folder that has a poser.exe file in it - even if it's a 0 bytes file. And so on.

Anyway, Poser not only has system requirements, it also has some user requirements as well. Handling "progress" seems to be one of them :-)

- - - - - 

Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though