I once heard a pretty funny
anecdote on this. Seems that back in the days of
mini computers, a computer lab had just gotten a new
terminal, and it behaved
very strange: the guy who would have to use it couldn't
log in when he was sitting in front of the terminal. But when he wanted to demonstrate it to somebody else, that person could log in just fine. He tried again himself - and could log in too! He sat down again, looged out and tried again -and was denied access. Now it got weird. He tried many times, and always, without fail, the terminal didn't let him in when he was
sitting in front of it, but worked fine when he was
standing.
WTF?? some sort of freak problem with electrical potentials that changed with the position of the person in front of the terminal??
Well, turns out the explanation was much easier: two of the keys on the keyboard had been switched (or wrongly labeled), and the operator was a touch typist when sitting down, but not when standing up...