I have a Lombard with built in DVD (onboard decoder).
I was playing a movie, when suddenly the AppleDVD PLayer stopped playing. I figured I would quit it and restart the software.
It won't start up since, it is giving back the following error message.

Apple DVD player cannot open because it cannot find required hardware. Try reinstalling Apple DVD Player (204).

I reinstalled the software, reset everything I could. PRAM, PowerManager, rebuilt the desktop...etc.
No luck. It sees, reads, mounts DVD discs, but won't open the Apple DVD player application.
I have the latest extensions and every extension I need according to the Apple TIL.
I checked the Apple System profiler to make sure that my DVD decoder was still fine, and it says that it is there.
How come the Apple DVD player cannot see it, or use it?

Help please!!!

[bipto]

I'm sure you already thought of this, but did you try applying the DVD-ROM update 1.0?

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I had this exact same problem with my bronze PB 400/DVD.

I found the solution by accident in my case. If Appletalk is turned off for any reason, you get this error message when attempting to run DVD's. Don't ask me why, but re-enabling Appletalk works everytime in my case.