Hi I have a 24inch LCD ACD display connected to my Mac Pro. This display all used to work OK, but now, read on. I had to send this 24inch LCD ACD display away to have the panel replaced. Since it has returned when I look in About This Mac/Displays it shows that I have an iMac connected as the display and now the brightness cannot be controlled. Seen one other with this problem on another forum, and have tried to contact him to see if he solved this problem, no reply as yet.... ADDITION : If the 24inch LED ACD is connected to my Macbook it all works as it should Thanks.