I created many DVD-R's before and never have problem. Recently, I suddenly started to have problems: the DVD-R's I burned cannot be played either on my computer or on my DVD player, even though the program says "your DVD was completed successfully". I did not change the program. The same computer can still burn playable CD's. The DVD player can still play my DVD-R's made before the problem started. I suspect the discs were not finalized since I cannot see the burned tracks on the new DVD's; they are all shiny like the blank discs. What is wrong here?