V3 shouldn't load automatically when you start Poser 4. Unless somehow you have set that as your starting preference. Try starting Poser 4 and if it's stable, click the Edit menu, then General preferences. Then choose "Launch to Factory State". Exit. Then start P4 again. It should show as it did out of the box. Then try loading V3 and follow instructions above. I don't think P4 is corrupted yet.