I have/had a similar problem with my car....it's worse in the winter or a heavy rainfall. I would hit a certain speed, usually >80km/hr and both the ABS and TC light would come on. I would shut car of and no lights until I hit a certain speed again. What I did was take a multimeter and hooked it up to my sensors. I then drove the car and read the AC volts the sensor was picking up. It turned out one of my rear sensors was getting a higher number than the other and I figure I have either a faulty sensor or exciter ring on this side. The light's gone away now so I am not too concerned.
