I have the ame problem with VHS burnt onto DVDs usig a PC. At least I can get them to play in OS9.
Apple techs seem to ackniwledge the problem, but the only solution they come up with is to burn the disks again using a Mac. The tech implied that they cannot support every burning software and platform on the Mac, and drew the distinction between Apple complient and Apple compatible.
Can see the argument with hardware, but then hat is the difference between DVDs burnt on PC and DVDs you buy in the store? Are there so many formats to burn a DVD?