When you say it works are you using the Play DVD from the menu, because that works for me to. The problem I have is specific to no dialog popping up asking if I want to play the DVD whilst watching fullscreen TV when I insert a DVD into the drive.
Dialog is not shown if something else is playing and that is how it is meant to be according to code and its explanation. Why it is prevented I don't know - easy to fix if so wanted.
I think it should be fixed but I don't know why it would had been stopped in the first place. I would of thought if you didn't want the dialog to appear you would select the option in the configration to have no autoplay, never ask.
If this is not fixed then I think a note or something needs to be added to the configuration screen to state the way this works because it is confusing. Or maybe another option would be to add another item to the drop down list allowing autoplay, ask everytime when nothing else is playing.