Bare spots in any of the insulation, possibly wires touching.
If the car starts fine, but when you shut it off and won't start again, check your battery terminal connections. My lincoln did this it seemed like forever until i checked it out one day. hasn't done it since.
I am absolutely sure that Midlife can and will explain this better but I'll give it a try /forums/images/icons/wink.gif The main thing is that a "short" is an electrical path between two places where you really want no path to be.
Corrosion can also cause a short to ground or between wires. A visual inspection for corrosion in the terminals and wire bundles would be helpful. If you suspect a short between wires or a short to the chassis (ground) then the best thing to do is use an ohmmeter to check for a resistance path. An open reads like infinite resistance on an ohmmeter, a short will give you some finite resistance reading. A resistance of zero means a perfect conductivity path but you normally won't get a a near-zero reading for a short - it usually will read something greater than zero but less than infinite resistance. If you need to test like this make sure you isolate the suspected wire bundle from upstream or downstream ground sources in the alternator/regulator because otherwise if you check for ground you will read a path through other sources. If you suspect a short between two wires then measure the resistance between the wires when the bundle is not hooked up to anything.
Really a visual check for corrosion and wear in the suspected wire bundle should do the trick. Let us know what you find!