How can I tell if DVD/CDRW drive defective?

[PaulS]

I have two Thinkpad T40's, one with a Matshita UJDA 745 DVD/CDRW drive and one with a Toshiba DVD-ROM SD-R9012 DVD/CDRW drive. When I use InterVideo WinDVD 4 to watch video DVD's on the system using the Matshita drive, sometimes the software locks up at specific scenes. Originally, I thought the problem was with the DVD ROM disk but if I replace the DVD/CDRW drive with the Toshiba one, the Thinkpad and software no longer lock up using the same DVD ROM disk. If I use the Matshita DVD/CDRW drive on the other Thinkpad using the save DVD ROM video disk, I get less frequent lockups at the same scences.

Based on these observations, I can only conclude that the Matshita drive is either defective or for whatever reason cannot read all the contents of this DVD. Incidently, I have already updated the Matshita firmware to 1.03. Is there any way to conclusively determine if this is a problem with my Matshia DVD/CDRW drive or a design issue with this particular DVD/CDRW model?