Extreme Problems Copying Wav Files From Dvd, the stupidity of incompatibility Options

[Chris the Produc...]

Hey there!

I'm new here, but desperate!
Here at the studio we use G4 MAC's with OS9. It has the standard DVDROM built in, so it's not all that brandnew, but usually stable as hell.
Right now I've been getting alot of errors when I try to copy WAV-files from DVD+ to the MAC. There's one MAC that even doesn't recognize the media as to be a DVD (it asks me to initialize)!
Now there's a note to this:
All these DVD's are burnt on a Windows PC. I KNOW these DVD's are readable and usable, 'cause ANY other computer, including G5's will read and copy them.

So, in short:

I get errors saying that some files are corrupt or unreadable (while they definatly are NOT - when I open them on a PC and burn them on a CD I can copy the exact same files to my MAC) and the other drive just doesnt recognize DVD's, although it IS a DVD Drive.

Do I need an update or patch on the software? Is my Drive too old? Am I not burning the DVD's right (some myth goes arround that you need to 'close session' when burning on PC to be read on MAC)?? I need a practical soluttion here, so I hope that this is no rare problem!

in other words:
HELP!!

thanx a mill. in advance!