iOS 4.2.2 build 8F305 (based on iOS 4.3) for Apple TV 2G is now available for download. You can download iOS 4.2.2 for 2nd generation Apple TV from the link below.
How to Update Apple TV Firmware
To update your Apple TV 2G firmware to iOS 4.2.2 (4.3), Simply go to: Settings > General and hit Update Software Updates and then Download and Install. You can also download iOS 4.2.2 from the Link below and update your Apple TV 2G via iTunes.
Download iOS 4.2.2 for Apple TV 2G
Full Changelog for 4.2.2
Addresses an issue in which audio is not output when playing some video content.
Addresses an issue in which video is not displayed when playing some content.
Audio output setting
Adds an audio output setting for switching to 16-bit audio for compatibility with some TVs and AV receivers.
Live FF/RW improvements
Improves the performance of fast-forwarding and rewinding live events.
Addresses an issue in which the description information is not displayed for some movies.
YouTube video order
Addresses an issue in which YouTube subscription videos were not ordered by date.