I had this same problem that just started a recently. I tried most of everyone's suggestions, switch cable, turn off, reset, all FAILED. My last resort is to buy a brand new HDMI cable which I have not done.
In my case, it came to mind that probably my apple TV's connection via wifi was weak. So, I connected my Apple TV to my mobile hotspot just to test it out and viola! I was streaming Netflix, hulu plus..etc.
So I reset my wireless router as new connection. Changed network name and password during the process. Then, connected my Apple TV again via wifi and sure thing.. it worked! Error free up to this date.
Just give it a try, if it doesn't work I can just assume that its a hardware issue.