Second monitor disappears Windows 7

I have a dual monitor setup with a Gateway FX6801 desktop computer with nVidia monitor card. Both monitors are connected with DVI. Both monitors were working great until today when the second monitor would not display. They both appear and are identified, but changing the Multiple displays does nothing to bring the second monitor back to life. Have tried everything to no avil. This happened once before, but resolved itself after several frustrating days.