What is the brand and model of your dvd burner?
My guess is the media. Princo, Ritek (G05?) and shintaro (never heard of it) are bad ones. You need to get a better media, Taiyo Yuden or Verbatim. If that is too expensive then get Maxell, Ricoh or TDK. Among 200 dvds you've burn, how many of them are still working without problem (pixellation, skips, etc)? Try to test the old backups. If, say 100 are still good, it's not about wasting 100 cheap media but consider your time backing up and burning 100 originals. Got the idea? Hint: use quality media and good dvd burner.