27" Cinema Display iSight not connected

I just bought a 27" Cinema Display to go along with my new Mac Pro, however after hooking it up and using it, when I open photo booth or facetime Im greeted with the awesome "No Camera Connected" message. Display has a built in iSight, but I can't figure out how to hook it up. I have everythign up to date, and can't find any other solutions online other then that. Help please? and Thanks in advance!