I'm no expert and may be wrong, but forget viruses, they attack OS and registry files not Mr Dorks weenie. My guess is P4 man object file has somehow corrupted. I lost some files in Poser once and took advice from the guys here and just re-installed the program over the top without removing it. They assured me I wouldn't lose any of my libraries but Thomas by name and by nature I still saved a lot of my characters and props to Zip and CD. However everything went as they predicted, the backups weren't necessary and everything worked fine again. Another thought I'm not sure about that genital prop you mentioned but it may have a bearing if the file is in the wrong folder or are you using a Mike object on P4, also did you turn off genitals on the figure? or make it invisible? You used the word "hidden" if object/properties menu/ hip = invisible there goes your lost hip! The correct way to hide his objet-de-art is go to Figure/menu and uncheck Genitalia. These last thoughts are probably the first points to check before a re-install routine. Incidentally I'm impressed, only 150 meg ram and 20 gig hard drive here.
Hope that helps, Tommy.