Most of the problems with your Apple TV (ATV) can be solved by a simple reset or reboot.
Resetting the 2nd generation Apple TV is simple; however, I always forget the remote combination to do it. Occasionally, my device will lose it’s HDMI handshake. A simple reboot fixes the process. Likewise, if the device becomes unresponsive, a reset frequently fixes the problem.
As far as the ATV is concerned, a soft and hard reset are exactly the same. The device completely reboots the OS no matter what method you use.
To reset your Apple TV, press and hold the Menu and Down keys for at least 6 seconds until the white light on the ATV rapidly blinks. Let go of the buttons and the device will restart.
Alternatively, you can just unplug the device. Let it sit several seconds before reconnecting power. The device will restart with a full reboot of the OS.