Bought a couple of HD shows from iTunes today. They play fine on my Apple TV, streamed from this iMac. I can't play the files on the iMac itself. I got the HDCP warning the first time, and get no video. Also, HD shows I purchased on my PC, which I've moved over, don't work either. The iMac is a 21.5 " with the i7 BTO. I have no external monitors attached to the Mac. I have a support case with Apple about it. They're stumped. Anybody else have this issue? Thanks. Brian.