I have backing up my personal DVDs for approximately one year using MTR, DVDoneX, and Toast. Recently my backup DVDs wil play on the computer, but not my stand alone DVD player. My media has not changed. The only change I can recall making is the upgrade to Toast 7 from Toast 6. My Sony player gives an error message (C: 17 30 dirty disc). I know it isn't a matter of the disc being dirty. Any ideas will be appreciated.