I've got a 2002 Kia Rio that will not start. It started as an intermittent problem: when the key was turned to the "on" position the lights, radio, etc would all come on, but when you would try to start it nothing would happen. After a few weeks of this on and off, now it won't start at all. I've replaced the ignition switch & the starter, and the battery is good. What could it be?