All of a sudden a few days ago, I realized that my keyboard was not working. It was plugged into my 23" ACD. So I unplugged it and put it into my Mac Pro. It worked. So I decided that my ACD's USB ports were not working. A phone call to AppleCare and he told me to take the display for repair to the Apple Store. I just did that, and the USB's worked fine in the store. I take it home, still does not work. So I thought my USB ports on my Mac Pro must be bad. But everything else I plug into all three of the back ones works just fine; but my ACD does not. In the store, he used all of my own cables / power adapter. What the heck? Why is my USB not working for my ACD but it is for everything else?