Can't tell you how to repair it until you diagnose the problem. Common failure items are the brake cutout switch, pressure switch screwed into the master cylinder, and the clock spring. That is a wound-up ribbon cable in a plastic housing under the steering wheel.
As the clock spring comes apart, eventually the horn will stop working and the air bag light will turn on. Measure the voltages on the two wires to test the switch on the master cylinder. Both should have full battery voltage when the brake pedal is released. If both have 0 volts check if the brake lights work. If they do not, check the fuse. There is a different fuse just for the cruise control. Check it too.
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Saturday, May 21st, 2011 AT 9:40 PM