What was found
JAN - FLIGHT 2395, THE CREW REPORTED SMOKE IN THE COCKPIT AND CABIN WITH THE APU RUNNING. CONTRACT MAINTENANCE INSPECTED THE AIRCRAFT, AND PLACED THE APU ON MEL 49-00-00, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. THE AIRCRAFT RETURNED TO IAH ON 04/27/07 WHERE MAINTENANCE REMOVED AND REPLACED THE APU, OPERATIONALLY CHECKED WITH NO DEFECTS, REMOVED THE MEL, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.