A few minutes ago Apple pushed a minor software update for the Apple TV 2nd generation. The firmware file, available for download here, is labelled 4.2.2 (build 8F305), but we're pretty sure it'll follow another nomenclature in the internal Apple TV settings or Apple's website, as with previous releases. iOS 4.2.1 for the second generation Apple TV was released on March 22 with various fixes including TV compatibility and audio improvements.
Apple's official Downloads webpage hasn't been updated with a changelog yet, so we'll update this post as more information about the update becomes available. [via]
Update: Here's the full changelog for 4.2.2. As expected it contains various bug fixes and stability improvements.