Screen turns off, will come back on

My friend's Dell Inspiron laptop is set to turn off the monitor after 10 minutes. Once that happens, we cannot get the screen to come back on again, hitting any keys or mouse buttons, or even tapping the power button, does not do it. It is not asleep or hibernating, the power light is lit and hard drive is spinning. Have to force a shutdown. I know I can tell it to just not turn off the...