This document explains the idea behind the 'Five Whys' option. It gives examples of how it can be used to identify the root cause for certains events or problems and how its apparent simplicity can easily lead it to be used incorrectly.
"Too often, people stop at the first or second simple answer, blinded by the symptoms or settling for the first ‘apparent’ cause. The first ‘cause’ offered is almost never the real root cause. And only when you find that can you take really effective action to remove the cause and so prevent the problem cropping up again. " - Intelligent Quality Management (2008) p2.