There's that pit of the stomach feeling when the computer goes black, when you think of the cost and especially the inconvenience of replacing a computer. This Mac has been working perfectly for 4 years but today it just quit. Wife whimpered for help. I'm a poor source of tech support but I'll try.
Fret fret fret
Why has the wired mouse also gone to sleep? Power! the UPS has bit the dust! nope, the power cord has fallen out of the back of the machine. Phew...resume happy monitoring.