I looked at the checkerboard and the stump in a hex editor. There is what I assume is a Mac file header at the top, followed by the normal Poser stuff and then the non-printing stuff at the end. The telltale keywords at the end "preview" and "PICT" indicate that this is probably the thumbnail image in PICT format that the Mac uses instead of the Windows Poser (pre .png) .rsr files. I have no way of knowing if any of this is garbaged but stripping it out leaves a .pp2 that loads fine in Windows Poser - without a thumbnail of course. Assuming you're not running Windows Poser on a Mac under emulation, I'm not sure what the problem might be. Try the PC versions as suggested. You'll probably have to make your own thumbnails, but at least it "should" work. If there's a Mac form here you might ask there.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken