How Ironic. Can't really help you. But i got a _NEC DVD_RW ND-3500AG.
It does not read any original dvds. It reads CDs with ease, tends to read burned DVDs after some tries, but does not read silver original disks. I suspect some software issue as I got these problems since moving from an Win2k based AMD system to an WinXp based Intel system. I got Assassins Creed and Fallout 3 on my desk, but can't install neither of them. I got the same drive twice, and both fail, thus it is even more likely due to a software issue. I've just browsed the web and the list of solutions and different attempts is rather long. Currently I'm thinking about mounting one of the drives into another computer, accessing that as a network drive. Though I'm not sure whether that would help. If you got a laptop, connect it your computer and access the drive over a lan network.