Just chiming in to let you know you’re not alone…
I have the same problem. I also have a Sony DRU-500a that works flawlessly.
For instance, bring up Nero, create a DVD video project and burn it on a DVD-RW using the Sony, no problems playing. Next, change the burner to the Lite-On and burn again on the same disc (after erasing it), the stand alone player says that it can’t play this type of disc (it knows something is there but won’t play it, but it’s not a region error.) Burn the same disc again with the Sony, changing nothing except the drive, everything works again. Sounds like a firmware problem to me. The book mode shouldn’t do anything since that’s for +R media, right?