Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)
Yeah ATV software version 4.1 is iOS 4.2.1
When you're in that menu, press enter twice on the remote and it will tell you the OS version.