ACER 22" monitor flashes on at PC sta...

My Acer 22" widescreen monitor, used as a 2nd display for my IMAC, worked fine for about a year. Then one day when I powered up my computer, the Acer display flashed on for about a second and then went black. I hooked up a different external monitor, which worked fine, ruling out (I think) a problem with the IMAC. The connections on the Acer all appear to be solidly plugged in. Pressing the Acer's Menu and Auto buttons do nothing. Turning the Acer off and then on again from the Power button (with the PC on) brings up the Acer green name logo for a second, then the screen background flashes on for a second and then goes black. Thanks in advance for any help.