Focus Starting Problem

I have a 2003 Ford Focus ZTS, and when I put the key in the ignition, it will turn but the car will not start. It has power (all of the lights, radio, and dashboard lights come on), but the engine will not turn over.

Even when there is not a key in the ignition, it makes the sound that usually means that the lights are on or the key is still in the ignition after the car has been shut off and the door has been opened. It is a continual noise in lieu of a beeping noise, however.

I have just replaced the starter in the last four months, and the transmission was replaced in the last three. The battery is less than one year old.

Is this a problem with the ignitions switch? I did have to have it replace about 2 years ago because it had locked up, which is apparently a very common problem with the Focus.

Car Info:
Make: Ford
Model: Focus ZTS
Year: 2003
Mileage: Approx 90,300
Engine: 2.0 liter