You know the way technology breaks down just when you really need it, and work the moment a technician arrive to see what's wrong? I have taken the consequences of that for years, and when ever I try to do something in a lecturing hall I bring a technician right away, rather than run to find him or her later.
However, technology has other, more devious ways of getting at you. The most mysteroius one, which I am certain is related to poltergeists and other paranormal activity, is the "bad contact". A contact error can occur in any part of the machinery, and it can occur at any time. Since it's a paranormal occurence, it will occur when it is really annoying and humiliating, and it will not occur when there are sceptics or non-believers present, who might isolate a scientific or rational reason for the error.
There's a "contact-geist" in my desk-top. It is driving me slowly insane - but the intensity of its activity is increased now, and escalates the closer I get to the defense. Thursday, I don't think I dare turn the computer on at all. I hope finishing the defense will exorcize it.