One thing I've found is cross runtime issues.  I normally have about two dozen runtimes.  I keep each character generation in it's own runtime.  eg: a gen4, LF, LF2, Dawn...

I generally only have open the runtimes relevant to whatever I'm working on.  For instance, I usually don't have LF open when I'm working on toon stuff.  

Of course, installing only takes place in one runtime.  But Poser will look for files in all the runtimes you have open.  (It would be nice if the "remove from the GUI library" didn't also remove it from Poser's awareness.  But baby steps :)

 This really comes into play when I open scenes.  i have to make sure the runtimes used for everything in the scene is open.  For instance, let's day I used a LF, V4, a building (in another runtime).  I have to have all those runtimes open when I load that scene.  That's why I settled on generations.  I commonly used a4 textures on v4 body.  Or morphs as well.

I ran into the same thing when I was deduplicating to hard links (saves heaps of file space).  Have to dedupe only within a runtime.  Otherwise, things can break when you close one.  

You might get that error if the runtime where the texture is in not in Poser's library list.  But then it should notify you that some content was missing.

All sorts of issues are why I keep runtimes very separate.  From P8 on.  Everything in it's own.  And nothing is added to the default that came with the poser version.  This keeps the installation (and its content) clean.  If i have to reinstall, it touches nothing I installed after.  Decades of painful experience led to current setup :)