Try taking a look at the "More Like This" section to the right of your post to try to find a solution.
The only thing I could think of is to unplug both devices in question, and taking out the HDMI cable and switching what ends go into what device.
Seeing related posts in the right column here, I found a post stating all Sony HDTVs are HDCP-compliant. Searching on that string, I found:
A FAQ that states, "Yes. All Sony televisions with a HDMI connection support HDCP."
Other posts suggest getting another cable, completely powering everything off, attaching the new cable, and powering up. Some have had success. It's worth a try. I would think the Apple cable would work with Apple TV though.
If you can play HDCP content from your Mac to the Apple TV without getting the error, then it's unlikely that you'll have a problem with your cable or HDMI connection. If the problem only occurs between your iPad and Apple TV, then I suspect your problem is with your network or the connection between the two devices.
Thanks for the additional suggestions.
My current testing routine was to go to Apple TV > Settings and select Sleep Now. Then, power off the TV. Then, either turn off the power port (wall socket), swap the cable, etc.
After the first attempt after my post and seeing 'power down' suggestions, I was able to get the first 4 seconds of the video to play from the iPad. I am guessing then that Winston is correct about network weakness. The TV wireless status window shows 2 of 5 bars, while the Apple TV wireless status shows 5 of 5 bars. Time to drag the router out into the hall again. At one point, the TV showed 4 of 5 bars.
Unfortunately, on my next iteration of testing I only get a black screen for Apple TV. Powered down for several minutes, unplugged cables, etc. with the same result.
I soldier on... thanks guys. I'll keep you posted.
Obviously, Apple TV is a beta product. We are the testers.
I spent several hours testing access to media I purchased, legally of course, from the iTunes store. Attempting to play from the Apple TV > Computers > MyMini via Home Sharing. (I also tried accessing from our iPad 2.) I found I could play a couple movies but not a couple others. All were purchased in the iTunes US store awhile ago and play successfully on the Mac, iPad, or iPod. (I even connect the iPod to the TV via the Apple cable for successful viewings on occasion. The TV doesn't mind.)
It is possible that the movies that don't play were on discounted sale in the iTunes store as they had been out for quite awhile and I took advantage of the the promotion. Could this be a possible reason for seeing the dreaded HDCP error on those films? Bizarre, if so. But, there are so many things that get the HDCP error with no rhyme or reason why, I don't think that is the issue.
I also found that even using the main Apple TV interface gives conflicting results. YouTube videos play, Vimeo does not. Podcasts play, trailers do not. (I have in my notes that from the iTunes store I can successfully view trailers but that might be from the iPad connection or my Mini/Home Sharing connection. See what I mean about conflicting results?)
I have done the usual, suggested power-off, etc. routine to see if it changes anything. It does not.
Since I ran an Ethernet cable to the Apple TV, the network is reliable. Since I can watch entire TV shows or movies and access other content, the HDMI cable and connection are not the issue. I thought it might be that the iPad 2 was not HDCP certified, which would be stupid, but when I stayed with only the Apple TV menus and found such problems, I now believe that the entire Apple TV ecosystem is suspect.
It is really too bad that the MPAA insists on crippled hardware for legitimate customers while the pirates happily work-around any restrictions. I rarely go to the movie theaters anymore due to the "20" minutes of commercial advertising before each film.
I am fairly sure I will be headed back to the store with the unit. I see it as unreliable, crippled, and have no confidence that if I purchased or rented a film that it would go well. Too bad. Here in Australia, I have Telstra T-box that provides films for rental and it works just fine with a more limited selection.
I solved my Apple TV problem. Simply, I replaced the cheap Apple HDMI cable with a high-speed HDMI cable from ConcorD.
I ran through another testing session with no change in behavior. I even tried an HDMI-to-Composite-Video converter with the same results. I then swapped the Apple HDMI cable end-for-end and everything worked! Since that made no sense and I didn't want to fiddle with it when it might go out in the future, crawling around sorting cables, etc., I simply got a high-end cable.
Apple should not sell inadequate accessories. It makes them look really bad. (See my previous posts here.) Their cable's diameter is about the same as cotton binding twine. The high-end cable is thicker than a pencil. Plus, as I was researching online and running test sessions over several days, my frustration with Apple (and the infernal MPAA) grew.
Things work great now but it will take several days before I can completely relax.
Thanks to HuskyN for the end-for-end suggestion. It didn't make sense but when it worked, it pointed me to a successful outcome. As I mentioned, the problem was reliably intermittent, if that make sense, as it played some content but not others. I now attribute that to cable flakiness.
P.S. Still, here's hoping the MPAA resolves their cranial-rectal insertion problem.