The latest Apple TV Update (version 5.1) is causing headaches for some users. According to a report on Apple Insider citing a thread on the Apple Support Communities website, many of the popular small iOS-based Apple TVs are getting bricked after running the updater.
Once the software update has been run on the Apple TV, users are greeted with a blinking light on the unit and a black screen on their HDTV. One possible fix noted in the Apple Insider post is to manually downgrade the Apple TV software by downloading an IPSW file from Apple, tethering the Apple TV to a Mac or PC using a micro-USB cable, and then restoring the software through iTunes.
Apple TV 5.1 appeared on September 24, 2012, but the support discussion has been growing steadily since that time as owners take the time to upgrade their devices.