BenQ 1650S and DW1620 - DVD playback problems

I use a BenQ 1650S DVD-ROM (OEM) drive and a BenQ DW1620 (OEM) in my machine. The firmwares I have installed on each are 5.HV and B7P9 (RPC1 by The Dangerous Brothers), respectively. I own hundreds of authentic U.S. DVD movies, but there are several which do not play in these drives for some reason. These discs will play without any problem on my laptop’s optical drive, a Sony CD-RW/DVD-ROM CRX830E, and also my PlayStation 2.

Strange things will happen when I try to play these discs in my BenQ drives. First, the DW1620 has better success playing some of these discs than the 1650S. When I insert one of these discs into either drive, the drives are able to recognize that I’ve inserted a DVD movie and it automatically loads my DVD player InterVideo WinDVD. Then the drives either constantly try to read the disc with the hard drive light staying on constantly or the drives give up altogether. Sometimes, my 1650S will disappear from My Computer completely as if the drive never existed! How weird is that?

Anybody know a fix for this? Could this be a physical problem with BenQ drives reading certain types of DVD movies? Should I try different firmware, software, DVD decoders, etc? Any help with this matter would be greatly appreciated. Thanks!

Editted to add: I have also tried InterActual Player. It helped for one disc, but not any of the others. Also, I can sometimes (very rarely) get one or both drives to play these discs, but this is just luck as the drive seems to “catch on” to the disc and start playing it after taking as little as a few seconds to over 10 minutes trying to read and start playing the DVD.