Do you have one of the keys with the grey rubber at the top? It has a chip in it that has to be near the ignition for the car to start.
Maybe that chip got damaged resulting in the car being unable to start.
Learned this when I went and got my girlfriends car key cut for here dodge neon, same kind of key. Got one without the chip, key would fit, open the doors, go in the ignition, but not start the car.