I've got a 2012 Mac Mini Server Quad-i7 and two monitors. Sure enough, unplugging the 2nd monitor (which is the Thunderbolt/Mini-Display Port jack to HDMI monitor) got it working (primary monitor is HDMI to DVI adapter). Both monitors are HDCP compliant so it's absolute nonsense. A soon as I plug the 2nd monitor back in the video stops with the same error.
I've had similar issues with iTunes, though. The 2nd monitor isn't quite 1080P capable and the primary one is. I have iTunes set to download or rent the 1080p version of movies (I have 3 Apple TVs so this makes a lot of sense). iTunes, however sees the secondary monitor and for some reason forgets about the primary monitor or the possibility that I might have other displays (Airplay and AppleTV) and informs me it will NOT download the 1080p version because my monitor is INCAPABLE OF DISPLAYING 1080P. First of all, that doesn't matter. OS X will scale 1080p to 720p or whatever you're using regardless of the monitor's capability and this monitor is between 720p and 1080p so it would still be better to scale the higher resolution version to it plus we're talking about downloading a file that will stay in your library (who wants to download the 1080p version at a later date and the pain that involves?)
So to download a 1080p movie, I have to disconnect my 2nd monitor and then iTunes is fine with sending me the 1080p version. I can then hook that monitor back up and low and behold, the 1080p movie plays just fine on the 2nd monitor Apple tried to tell me was no good for it (even though that's the secondary monitor, not the primary one).
There's the kicker, though. The Mac Mini defaults at boot time to the Thunderbolt port if you have two monitors plugged in! There is no way that I have found to tell the Mac to make the HDMI jack the primary monitor jack. I can't just switch the adapters because even though it "works" the main monitor gets some kind of noise crawlies on it when I use TWO ADAPTERS (i.e. Thunderbolt/MDP to HDMI and HDMI to DVI) to make it work with that monitor. There is no Thunderbolt/MDP to DVI single adapter I'm aware of. The other monitor is quite happy with HDMI to HDMI or Thunderbolt/MDP to HDMI adapter). So if I need to see the boot drive selection screen, I have to turn on the second monitor to m left (main monitor is in front of me). I don't know if having the larger monitor as the Thunderbolt/MDP connected one would get rid of the problem or if it's just having two monitors with one of them lower than 1080p resolution that sets the bug off.
I can't help but see these two issues as related. In both cases, the problem is solved by disconnecting the 2nd monitor! What is wrong with Apple's operating system that the 2nd monitor is interfering with programs on the primary monitor? Shouldn't it just be looking at what it's connected to rather than considering what else is connected to your system? Someone on here says the problem is political or something. That's nonsense unless you think Silverlight should be the default. Apple needs to fix their operating system so this is not an issue. Telling met it's HDCP when both monitors are HDCP compliant is just SAD. What's sadder is that Apple and/or Netflix has not fixed this problem in over a year now. That's RIDICULOUS.
Yes, I could switch to Firefox. I prefer Firefox, even. I NEVER use Safari as a rule. Why am I concerned about running it on Safari, then? It's because Firefox plays Netflix CHOPPY. I've got a quad-core i7 here with hardware 1080p decoding that uses less than 6% CPU playing 1080p movies. WHY would Netflix be choppy on this computer? It's far choppier yet in fullscreen on Firefox. I've seen the bug listed on Firefox's site, but no one is working on it (it says so and begs someone to take up the task but no one ever does). Then, there's Chrome. I refuse to install Google's SPY BROWSER here. That's like installing Windows 10 on your Mac. You're just handing your keystrokes and data over to Google or Microsoft, respectively with no privacy recourse what-so-ever. Believe it. How it's the most popular browser is mind-boggling to me. Kids today obviously don't care about their privacy in the least (or Facebook and Twitter wouldn't be so massively popular telling everyone what you're doing at every second as if anyone cared except perhaps thieves watching for a good time to rob you since you just announced you were on vacation 1000 miles away when you posted days of skiing photos on your Facebook page.