*Here's how to FORCE RESTART an Apple TV:*
http://methodshop.com/gadgets/tutorials/appletv-fix/
1. Unplug the Apple TV.
2. Wait 10 seconds (Try cursing at your Apple TV if that helps pass the time).
3. Plug-in the Apple TV.
4. Immediately point the remote at the Apple TV and press and hold both Menu and down ➖ on the Apple Remote. Continue to hold the buttons until the Apple TV has restarted itself 2 or 3 times. You will probably see a green flash on your TV screen when the Apple TV restarts.
5. You should now see a screen where you can select one of the following: Restart, Run Diagnostics or Factory Restore. Select Run Diagnostics from the Apple TV Recovery menu. If there's something wrong with your Apple TV, the diagnostics will tell you. Hopefully it's nothing serious like hard drive failure.
6. If the diagnostics say your Apple TV is fine, then select Restart. If your Apple TV fails the diagnostic tests, it probably has a hardware issue. Unfortunately there really isn't anything else you can do. If you recently purchased your Apple TV, then you can take it back to the store and return or exchange it. Also, your Apple TV might still be under warranty. Check your receipt. You might be able to get Apple to repair or replace it.
if that didn't work and you still need to FACTORY RESTORE your Apple TV, then read step #5 on this page:
http://methodshop.com/gadgets/tutorials/appletv-fix/