It's not the content that Poser 8 doesn't see, as long as you see the "shrugging man" your content is there. The issue is that Poser 8 does not use RSR thumbnails like previous versions did, so you need a utility to convert all of the older RSR thumbnails to PNG thumbnails.

Offhand, I can't remember the link to the utility that everyone recommends, but it will do batch conversions for you. I'm hoping someone else will pipe in that knows the link off the top of their head  (or you can search the forums for previous posts).