sounds like you have a play and charge kit
http://www.inglue.com/wp-content/uploads/2009/09/xbox360pnc.jpg ??? that cable right?
if your using a wireless controller you need this the wireless receiver for it to work
http://media.teamxbox.com/dailyposts/xbox360/xbox360-wireless-receiver.jpg
Good catch, I completely missed it.
I have said receiver and the charge kit and they are correct. If it was a "hardwired" controller my solution would work.