I have a flashing light on my apple tv. When I replug in the power a blue music symbol and some USB cord shows up.
Do you have something plugged into the USB port on the back of ATV?
No , nothing , just a hdmi cord & a power cord.
Sounds like the Apple TV is in recovery mode. Try to restore the Apple TV. Follow the appropriate link for your Apple TV for instructions on the restore process.
1st Gen - http://support.apple.com/kb/HT3199
2nd & 3rd Gen - http://support.apple.com/kb/HT4367
Restoring did not fix the problem. But it did waste a good portion of my night.
Retrieving data ...