I confirm that this is the case. Trying to establish with team if this is by design or is a bug.May sound strange but, make sure you have the Video plugin enabled.
RC1 or 2 can't remember which, had the issue that, for some people, without the Video plugin enabled, "Play DVD" did not work.
I have this same issue using RC6. Is this by design, or is this a bug??? to me it is a bug. I should not have to ahv the video plugin enabled to play a physical disc. And I use Moving Pictures for my stored movies. I do not need the Video plugin to be seen, or to use it. But I have to have it enabled to be able to play discs and images.
Same thing with music. the Music plugin has to be enabled to play music (which is ok, there is no other music plugin...). I think that is the case with music. I have not tried it since upgrading to rc6...