In the backdrop of so much of 21st-century life, computers are an unseen hand that guides the day in ways we rarely know about. Until they crash. Wednesday provided one such rude awakening for commuters in Montgomery County. A computer meltdown disrupted the choreography of 750 traffic lights, turning the morning and evening commutes into endless seas of red brake lights, causing thousands of drivers to arrive at work grumpy and late, and getting them home more frustrated and even later.