Radiant Boilers How can I fix it!?

my radiant combi boiler reaches it thermostat temperature and operates for about one hour with no probs. but when it trys to reignite it comes on for a split second and then trys to keep reingniting. After about 20 atemps the boiler finally reignites. Sometimes the red cut of warning light comes on and you have to press it to reativate the boiler......Any Ideas

A Lawson
November 2008