LCD screen is solid black

I have an interesting failure.
After finishing a successful print, I Cleaned and re-leveled it and started a new print. When I came back ( 1 day later) I found that the screen was not creating Masks, was remaining completely black and the machine was running as though everything was fine ( i.e. touch screen was showing progress, what was being printed and the Z axis was moving correctly). Has my screen control board gone bad or is there another failure here. Please help.