SO, I went to my modem website (I recommend you bookmark it), did a factory reset, then did a performance check. Download power should be +8 to -8, Upload power 37 to 55, and signal/noise ratio over 30 (higher better.)
Then I restored the Apple TV... and off she went.
I have had the cables unplugged so many times, and rebooted everything so many times, that I really don't know what made them happy again.
Guess: the router restore looks like the big help here. Try that. Thanks and good luck!
Had similar issues with my ATV2 not being able to set the date and time. I tried resetting, restoring, restarting and all would seem to get stuck at the setting date and time. I finally uplugged it and plugged it straight into my MacBook Pro with the micro usb cable (didn't even need the power cord). Through iTunes I clicked on Restore. iTunes took over and did a complete restore including a firmware update. Then when it finished it said to plug it back into the TV. When I did it asked me to set the language, set the wifi network and password (the usual startup stuff) and voilà! It works again.
Hope this helps.
I was able to get my Apple TV working again by downgrading the firmware following the instructions in this message:
In case that message disappears, here's my translation:
1. Connect your Apple TV to your computer via USB. Don't plug in the power cable.
2. Download the older 5.0.2 firmware from Apple here:
5.0.2 (Apple TV 2): AppleTV2,1_5.0.2_9B830_Restore.ipsw
5.0.2 (Apple TV 3): AppleTV3,1_5.0.2_9B830_Restore.ipsw
3. Open iTunes and select the Apple TV. Hold down the option key and press the restore button at the same time.
4. In the dialog that opens select the firmware that you downloaded.
5. The restore process will take a few minutes. Once it's done plug your Apple TV back into your TV. If the date and time message persists just press the menu button to skip it. This got mine working again.