Can't stream Netflix through Apple TV - "content requires HDCP for playback"

I have been using Netflix for a few months and all of a sudden it won't stream - I am getting an error message telling me the content requires HDCP for playback. It's never been a problem before and Apple TV itself is working fine. I have spoken at length to Netflix who are adamant that it is an Apple TV hardware problem. I've done all the troubleshooting suggested on Netflix's website and also via this community with no luck. I've also changed the HDMI cable and done a full restore of the Apple TV but still the problem persists. Any suggestions?