Unfortunately, when ignition switches go, they go without any forewarning.
If you have a set of small screwdrivers (the really thin ones), pop the steering column cover (four screws, two below, two behind the wheel - just turn it to access) and gander at the wiring block on the left side. Probably has some corrosion issues.
Odd as it may sound, I fixed the wires on mine and kept the OEM switch, and it worked again. I did not have a good experience with the aftermarket switch, as it wanted to start the car as soon as I reconnected the battery.
