The latest update on client, released on 7 March 2011 and the Beta server release 2.4.5 added support for AirPlay, which can be use with AppleTV 2G!
The catch is we have to wait till 11 March 2011 for 4.3 to be released on AppleTV 2G, finger cross!
Head up to Air Video Server 2.4.5-beta for the new server, and update your AirVideo app on your iDevice to enjoy.