I have a 2 year old aluminum 20 inch cinema display. It has this odd habit of going dark for days at a time. It shows its connected via the displays preferenace panel and I can move winsdoes to the screen in the dark. Just as suddenly its back on for days at a time. All connections are solid. I can rule out back light as the screen looks wonderful when it works. Do you think its the external power supply? Or the inverter board? Both very fixable items. Or something else? Any ideas?