I have this problem: I have a Liteon LDW811S writer, with the latest (official) firmware. I have no problems writing DVD's (I always use Princo's) and I can perfectly play all copies on both my stand alone DVD players (living room and bedroom) but I can not read them on any of my DVD-ROM drives, not even the Liteon writer which wrote them in the first place!
So, is this a normal behaviour? I think not. Strange that the computer can't read them, en standalone players can.
Just found out today, it's not a single DVD I'm having this problem with, I've tried all off them, all the same!