Apple TV with airplay not working

My Apple TV (model MC572LL/A) is intermittent when using Airplay with my apple devices. I have an iPad mini, a second gen iPad, and iPhone 4s, a 2009 iMac and just recently got a Macbook Pro retina display. Sometimes the airplay works when I enable it, but most times it does not. The common symptom is that my TV screen goes dark, or does not change at all. On my device it says it is connected to airplay but nothing is happening. And, if I wait a while, the initial screen from my device appears on the TV but locks with that display- even though I have turned airplay off on my device. Or- when trying to turn airplay off, it locks up and does not change state.

My Apple TV has a good internet wifi connection, working well with Netflix or for watching movie trailers or streaming a video or music from my iMac upstairs or from my MBP.

I have tried reseting the Apple TV, reseting the router, I have tried firewall on or off (and set per troubleshooting procedure) and I even moved the router so it was about 10 feet away from my Apple TV. I know when I initially got the Apple TV that it worked fine with our iPhone and with the regular iPad. I had some intermittencies with my iPad mini but ended up resetting the internet connection and that seemed to clear it up. I have also noted that when I activate airplay from my iMac (it is upstairs with the router and connected via ethernet) that I can usually get the airplay to work with the apple TV (which is downstairs and using wifi for its connection). It is not very convenient to run upstairs- activate the airplay- then run downstairs to watch 🙂. I have read and tried the airplay troubleshooting techniques- still having the issue. I have also turned off ALL bluetooth devices- still does not work. On the rare occassion it does work, it usually does not work the next time I try.

Any suggestions for things I could try? Thank you.

Mark