Was the pulsating coming through the brake pedal? If it was then it probably was the ABS. If you were on dry pavement and werent braking hard thats wierd that it kicked in. I have noticed that it takes little to get the ABS to kick in on my car. Have you ever heard/felt the ABS brakes in your car before? If you havent I would take your car down some dirt road and try it out, I did that just to get the feel of it, it was quite fun too.
2003 Volkswagen Golf GL 24,000 miles. 1.9L I-4 TDI 5spd.
1986 300E. 115,000+ miles. 3.0L I-6 1st daily ride, around town only. (Gone)