Acer monitor al1916w lcd monitor and power button

Monitor connected to a Dell Dimension 2400 via vga cable. Pc was starting correctly so it was booted in safe mode. After defrag, when the power button on the monitor was pressed, the screen would come on for a second and go off. After pressing the button several times, the picture would stay on. Different vga cable did not make a difference.

video drivers had been uninstalled and reinstalled. Monitor was doing this with just the monitor hooked up to the pc even before the bios was loaded. All diagnostic lights on back of the dell indicate all devices are connected after POST.