I want to use my Apple Cinema Display 30-inch monitor with a 5,1 MacPro and a 6.1 MacPro. I've tried using a StarTech SV231DD2DUA Dual DVI USB KVM Switch, but the monitor shuts down (the light fades off) rather than taking the signal. I'm trying to swap the cables around to see if that might be part of the problem, but so far, neither Mac will show up on the screen.