HD tv show download scrambled playback
So I have a 2 week old iMac 29", with Mountain Lion. I have downloaded 2 episodes of a TV show from iTunes, however when I go to play them back the screen is scrambled and pink/green with what appears to be the open Safari window flickering through. Other videos (non copy protected and SD) playback just fine.
I have turned off home sharing, made sure the mac is authorised, and tried opening the individual files in Quicktime player, which occasionally seems to work for one of them. I have no other applications running.
If I didn't know better I'd say this is reminiscent of a graphics card issue, but everything else is fine, and I suspect it's to do with copy protection. I tried to lodge a call with Apple's fancy support hotline - it rang me, then connected me to an 'invalid number' and asked me to try again. Awesome.
iMac, OS X Mountain Lion