suggest both you and triffid look up flame rectification it will give you all the answers you need
brian, February 2011
Its a flame rectification problem. The pilot flame heats a probe that is sensed by the curcuit board, then the board allows the gas control valve to open fully. Its gonna be the probe and or the curcuit board.
triffid, February 2011
pilot may be dirty or partially blocked the pcb isn't detecting the pilot light also check there are no shorts in the ignition leads
brian, February 2011
edit
I can answer this question...
My pilot light comes on, keeps clicking, but the burners won't fire up. Why?