Did you also have Poser 4 installed?
Have you tried to rename your Poser5 directory to something else? Poser alone i.e. And, if you also have Poser 4 to rename your Poser 4 directory too!!!
Do you have a "funny" file inside the Vue directory looking like a file with a sign in it I (and probably you) don't have on the keyboard and without any extension? If yes, delete it.

What you must obtain again is, when you try to import a Poser pz3 file, that Vue askes you to locate Poser.

Somewhere in the past HERE is the thread, a user had the same problem and resolved it.

Maybe this time?

:-)Guitta