Some years ago my friend experienced this story: He was a system maintenance engineer in a medium (~50 people) company. Once at night, when he was leaving republic, the director called him that the system is totally off, nothing works. Hi decided to get some informations by phone and asked the director to go into server room, switch the monitor and... "What do you see in the monitor?"
"There is 'Enter login name and password'..."
"Please, enter following login name and password: ..."
"I'v entered it."
"Hmm, please, try it once more... I will spell it..."
"The same. Nothing."
So my friend decided that the problem is serious, turned his car back and after a few hours was in the server room. Both login name and password were correctly typed. But nobody pressed enter.