Can anyone explain this? I saw this post in a thread about the Mac Pro and monitors: http://forums.macrumors.com/showpost.php?p=18692006&postcount=73 So it sounds like using an Apple adapter (I have Thunderbolt to dual link DVI) between the 2013 Mac Pro and an older monitor will cause HDCP to prevent iTunes from showing movies. But why? I've searched Apple's knowledge base and not found anything mentioning this. (To the contrary, Apple says in several places that their monitor adapters are HDCP compatible.) What monitors/adapters won't cause this error and how can I tell before buying a new one? Thanks in advance for any help or suggestions!