One of my DVDROM drives did just that. I changed the drive and the problem vanished. Since it still worked with factory DVDs, I gave the drive away after writing a note with a black sharpie pen on the drive.
Do try a LENS CLEANER before changing the drive.
Whenever I play a DVD+R in my Sony VAIO NV 170, it will freeze frame at different times. It is never in the same spot. OS Windows XP SP1 Media Player 9 updated and Win DVD and even Interactual Player.