Count me as one who never saw this error until I installed V4.  (Actually, the V4 pro bundle.)  Very odd.

I'm reluctant to delete the library prefs file, because I don't want to have to add all my runtimes again.  I've got a lot.

I wish Poser would let you add every runtime in a folder, like D|S does.  And that it would automatically alphabetize them.