One of the most common anti-lock brake problems is malfunction of the sensors on the wheels. This can happen as a result of metal particles being attracted by the magnetic parts of the sensor, and thus causing them to fail to give the correct signals to the computer. In order to stop this from happening, these sensors should be cleaned frequently. Failure to do this can result in the sensors eventually breaking down. You should also change the brake fluid to prevent moisture buildup. This buildup can cause the valves to stick. Putting on the wrong sized tires can also cause a problem with the anti-lock brakes.
For more info, see Small Car Safety: Are Small Cars Less Safe Than Larger Ones