I cannot view HD channels (from freeview HD box) through my Sony str-dh810. I've narrowed the problem down to something called HDCP. When HDCP is on, I cannot view anything from my freeview box. Turning it off solves the problem but seemingly when I switch to an HD channel HDCP is switched back on. I've tried swapping hdmi cables with no luck. Halp!

This piece of information should solve your problem:

High-bandwidth Digital Content Protection (HDCP) is a form of Digital Rights Management (DRM).
There is a licensing body that issues licenses for HDCP devices. Each HDCP-compliant device, like your Blu-ray player or Xbox, has a license and the ability to talk to the receiving device on the other end of the HDMI cable. The outputting device says "Hey display! Are you HDCP compliant? Here is my license, show me your license!" The display (or other HDCP compliant device) returns with "Why yes, I am legit! Here is my license!" When that process works, it happens within a thousandth of a second and you, the consumer, never even notice. You power on your Blu-ray player or DVR, it makes nice with your HDTV, and you live a happy life never knowing what HDCP even is.
if you have an older HDTV set that is not HDCP compliant then you cannot watch any HDCP compliant content on it. If you plug in your HDCP-compliant device to a non-compliant device, you'll either see a blank screen or an error message like "ERROR: NON-HDCP OUTPUT," "HDCP unauthorised," or simply "HDCP ERROR."
Short of buying a new television or giving up on your video game project the only way to deal with your HDCP compliance problem is to buy a cheap HDMI splitter that ignores HDCP requests.