I found my real skin shaders did not work unless placed in the same directory as the Poser version running.  For example, I run Poser Pro but take objects from Poser7.  I could not use python scripts, at least the realism shaders, from the Poser7 directory, but they worked if I installed them in the Poser Pro directory.  Also I found that when in the Vista operating system you have to have UAC turned off for some of the realism shaders.  Apparently no matter where you install them (for example I have all Poser stuff on my D: drive) some scripts want to access the C: drive and UAC denies access.  I don't know if this helps, but it has been my experience so far.