Shortly after LOC capture at KDEN in a -700BBJ, the A/P began commanding lateral excursions from right to left and back again, then reverted to CWS mode. Disconnected the A/P and flew the approach manually. FAA had no indications of LOC deviations. This was entered in the maintenance log.
Several days later after another flight, one of our VPs informed us that a fellow passenger was using his blackberry device around the time of the incident.
This sort of odd A/P behaviour is not limited to the 737, by the way.