boiler keeps turning itself off?

my biasi combi keeps turning itself off, the lock out switch comes on and it has to be fired up again, i noticed the pressure (bar) was to high and rads were making fuuny noise i assumed it must have air in it so i flushed the system through re filled and bled normal staning pressure 1bar it was ok for a while 2 days niw it's started again the boiler is 7 years old and has never ben serviced could it be it needs a good clean up when it lights it ignights like there is a bit off a blockage.

mo
February 2010