for your boiler there are 5 lights on the display
are you saying ONLY the shut down warning light LED 2 is flashing?
i 'll need to know if the boiler fails to light for CH as well as DHW
if the boiler fails to light for CH & DHW then the most likely culprit is the low water pressure switch
BUT
LED 5 normally starts flashing as well
need more info before i can properly diagnose fault for you
manwithnoname
May 2011