Both "Copy Once" and "Copy Freely" result in a blank screen for recorded TV. For example, I recorded to my DVR the A&E Star Wars Special. When I tried to record from my DVR to my Mac, it said "Copy Freely", but a blank screen appeared.
Live TV works as expected: "Copy Once" produces a blank screen and "Copy Freely" returns a the recorded TV as expected. I have successfully recorded multiple episodes of "Dirty Jobs" off of the Discovery Channel.