Does anyone use those DVD/CD repair/polishing devices? My Monsters Inc seems to keep freezing up on chapter 28 and I've noticed a small arcing scratch on the surface (probably from playing it in my portable DVD player). Do those repair things really work? Are any of them better than the others? I thought It might be handy to have one around.. especially with Disney DVD's that get taken off of the shelves for 7 years. Any recommendations/advice would be appreciated.