After the boiler had reached the desired temp the burner will cut out but the pump should remain on for i think 3 minutes with that model Boiler. This is to prevent the water left in the heat exchanger from getting to a temperature that will harm the boiler. The heat left in the heat exchanger is then disapated around the system instead of remaining in the boiler.
That is What should be happening. But if pump stays on for longer then 3 minutes then you may have a problem with the Controls.
Ste
March 2010