AppleInsider discoverd a growing thread at the Apple Support Communities website where users report issues after updating their Apple TVs (2nd and 3rd generation) to the latest Apple TV 5.1 software. It looks like many Apple TVs are getting bricked after running the update:
apple tv software update
At the event held today in San Francisco, Apple announced the new, third-generation Apple TV with a brand new user interface. According to Apple’s press release, second generation Apple TV users can install the new Apple TV UI via a free software update, available today. Third generation Apple TV hardware is required to play 1080p video.