I actually had the same problem, though not with a Contour. It turned out to be the actual ignition switch in the steering column. I replaced it and never saw the problem recur. Just a thought.

'99 Sport TropicGreen,Duratec, SVT exhaust, Brembo rotors, Ceramic pads, K&N filters(oil & air), Alpine CDM7874, Polk DB570 speakers front and rear. Fog light mod. 50% Formula One tint.