B757 flight crew experienced aileron trim changes as flaps were extended and retracted. Maintenance elected to defer repairs until aircraft arrived at next destination. The next crew is informed that the aircraft will not be repaired but continue with the MEL. After a call to union safety representative the aircraft was removed from service.

Narrative

With the logbook write-up signed off; deferred; we determined the best course of action was to operate the aircraft to our destination. I walked outside and down the crew stairs to inform operations of our decision. Operations stated that maintenance would check the flight controls at destination. My co-pilot flew the leg so I could monitor the symptoms and make mental notes. The autopilot was engaged during the flap extension to 5 degrees; the control wheel displaced 1-2 degrees right aileron input/trim. The co-pilot hand flew the aircraft during the final configuration of the flaps and approach. The ailerons where displaced between 2 to 4 degrees; stabilizing at 3 degrees for the remainder of the approach. Entered the write-up in the logbook. After exiting the aircraft; maintenance informed us the aircraft was turning and departing in 1 1/2 hours; and that the problem was to remain MEL'd. I called the union safety contact; and expressed my concern that another crew would be placed in the same situation without the current history; and the aircraft not being troubleshot prior to flying again. I received a phone call later that the aircraft had been removed from service. I feel let down by my management team! I felt my crew received no support; with one exception; with our concern on the condition of our aircraft after providing maintenance and operations with new information as it possibly relates to these items and the MEL item. 1) The aircraft flight controls not looked at in our departure airport after receiving new information concerning the malfunctions. 2) Maintenance Manger not understanding or acknowledging my concerns of possible spoiler float; first addressed by my crew after review fault reporting manual troubleshooting guide; flight controls. 3) The operations first offering a theory that the flaps could have caused the roll; then indicating that he 'Did not support our position' and implied that if we refused to operate the aircraft... 4) The aircraft being scheduled for a turn in approximately 1 1/2 hours; after being promised by operations; that maintenance in destination would investigate the malfunction prior to flying again. 5) Logbook deferral page not having enough space (in the computer entry) to enter the complete write-up; the ability to defer an item for a longer period; and the log page since being removed.