Martin made several Mac apps that change PC Poser related "stuff" to Mac files. Among the translators are some for 3DS & obj. I had this problem with RDS 5.5 not recognizing some obj files (created in RDS on Mac) not being "found" when trying to open them up again. I used Maconveter to make them recognisable again. You can get the app in freestuff (utilities) or here: http://www.soft-rabbit.com/