We have a WinXP PC that uses an ATI FireMV graphics card to display onto 3 monitors, 1 regular PC monitor, 1 small HDTV via VGA, and 1 bigger HDTV via DVI -> HDMI converter and HDMI into the TV. The problem we are having is only with the big TV connected via DVI/HDMI.
The PC stays on all the time, but the TVs get shut off overnight. In the morning, you go to turn on the TVs and the big one does not pick up any signal. It displays as if there was nothing plugged into it. The other two monitors take off no problem. What we have been able to do to "make it work" is to go into windows display properties settings, click the problem display, and uncheck the "extend desktop to..." box, apply, then recheck the box. After doing that, the TV will come up with the display. This leads me to believe that the problem is in the PC, as apposed to the TV. I've verified that the PC is not going into hibernate or suspend. This problem used to only happen once a month or so, but it has been happening every day lately.