Do you have a second generation Apple TV? Apple just pushed an update, firmware version 4.1.1 (the previous firmware was 4.1), build 8C154. The iOS remains 4.2.1. Yes, I know this is confusing.
Just to clarify: in the Apple TV’s About menu, hit the select button on your remote and it’ll cycle between firmware, and iOS build versions.
No list of updates have been included.