I have a 2007 Mac Pro that shipped with 10.4.7, and an ATI Radeon X1900 XT graphics card. The card has two DVI outputs for a dual display setup.
I recently updated my OSX to Snow Leopard and have never tried to connect a second monitor.
Now, when I try to connect a second monitor, OSX does not detect it. Any help with this issue would be greatly appreciated.