|Some people updating their Apple TVs to the latest firmware have found it rendering their set-tops useless, notes AppleInsider. Posters on Apple's support forums complain that following the update, an Apple TV may be left with a blinking light and a black screen. Alternately, the device may still work on a basic level but be unable to connect to a LAN, rendering it useless anyway.
The issue actually extends back to the v5.1 update in September, but is still ongoing. The only fix appears to involve connecting an Apple TV to a Mac or PC via micro USB, and then manually restoring from an IPSW file using iTunes.