It is finally here, an update for MCX for Xbox is available on Xbox Live now One of the most important changes is that now you will be able to play back CGMS-A content (HBO etc...). 

You should get prompted about the update next time you  log into Live.

For those of you who do not have an XBOX Live account you can request the update thorugh this link http://go.microsoft.com/fwlink/?LinkId=39479