Reseat the Graphics board.
Get down very low and make sure that those gold fingers are all the way in.
Make sure any PCI-e cable is fully seated in the Graphics card connector, as well as the back of a modular power supply.
Make sure your Data cable is fully connected to both Graphics card as well as Monitor.
If that doesn't work, try another PCI-e Slot if you have one. Or Try another Graphics card if you have one.
You can check your monitor, by turning it off then back on. Some Monitors, like mine will display a graphic without any signal upon initial power up. If you see the graphic you can be sure the Screen didn't kick out after it got hot.