I just realized that one of the MDP's on the back of my Mac Pro does not work. If you're facing the back of the Mac Pro its the one on the left, it has the little monitor symbol next to it. If I plug in my ACD to that port it wont work, it only works in the right side port. I'm assuming its just broke. Or does the left port only support a dual monitor? I wouldn't think so but want to make sure before I call Apple. Any help is appreciated. Thanks!