You\'re situation, although sad in it\'s own right, may not be all that odd. The ac \"power adapter\" for the Z is a switching power supply. Though these are generally reliable and very effective for this type of application, they can have a problem. In the simplest of terms, you could think of this power supply as a vibrator (no jokes!). With a marginal supply, it may not \'vibrate\' and will then supply no power whatsover. Very often, unplugging them (the only way to turn off this particular supply) and plugging them back in gives the supply a \'kick\' and it will work again. I have a laptop here with a similar problem.
I would suggest you plan on buying a new power adapter if it happens again. Once they start not working, it\'s usually a rapid decline into not working at all...