Hi Steve,

Although it sounds to us more like a problem with the hydraulic system somewhere, there is a known issue with that generation of Primera's ABS brakes. The ABS wheel speed sensor ring becomes detached from the driveshaft joint and the ABS sometimes is activated without the brake pedal being pressed. The fix is to replace the driveshaft joint.

Either way, I'd recommend bringing the car to a good mechanic, telling them that and then letting them inspect it.