Hopefully some QT and DVD gurus will come to the rescue here as I just tried some commercial DVDs with Mavericks that used to work properly with Snow Leopard 10.6.8. Mavericks is a mess.
Even some .mpg video clips in my iTunes won't work properly, and when they do, theory are somewhat blurry.
Do you have both QuickTime Player.app v. 10.3 in your Applications folder and possibly QuickTime Player 7.app v. 7.6.6 in your Utilities folder. I find QuickTime Player 7.app works better.
But things are crazy now, and clicking on a video clip in iTunes comes up with "This movie requires QuickTime, which is not supported by this version of iTunes." and clicking OK, the video starts to play in iTunes. *** is that all about???
On a commercial HD DVD, iDVD opens and I get the control bar, but hardly anything works: clicking 'Menu' flashes a Not Permitted sign, the Pause doesn't work along with many other controls. Again *** Apple??
Everything seems to work as expected using Snow Leopard and FWIW, I never use Launchpad.
I'll need to do some more checking with my own Mavericks setup, but again I'm not impressed.
What do you see in the DVD just using the Finder?