Alright, I fixed the issue. If your preview image is just purple, or transparent to a feed placed behind it, try going to "help" in Roxio and checking for updates. Yes, it's a super-obvious step, but Roxio never prompted me to update or suggested that there might be updates, so I just came across it myself. Download and install SP 2.0, and that will (hopefully) fix the issue. It worked for me, anyway.