Unsupported

HIi,

I've had an Apple TV since January and a few times my television has come up with an unsupported message when I try to turn the Apple TV on. Disconnecting the HDMI cable and reconnecting it has worked a few times; however, I can't seem to get it to work at all anymore. The HDMI cable works fine, I've tried it with other devices and had no problem. Any suggestions?

Emily