Could you tell us what software, if any, you are are trying to use for importing from the camera? It's possible that it doesn't recognise the Raw format (is it really DNG?) and just doesn't display them.
If you're doing it through the "My Computer" (or the Mac Finder equivalent), you should still see the icons for the Raw files, even if you can't see the thumbnails.
Have you got the SILKYPIX® Developer Studio 3.1 SE program installed? If so, can you import to that from your camera?