I have the same fault. Apparantly if the power to the boiler has been interupted it can damage the main PCB (printed curcuit board) I'm in the process of inspecting the old one for obvious problems before sending for a new one which are very expensive. If I can find what the problem is I'll be making a small charge for repairs to faulty boards.
Brian Dudhill
September 2012
glowworm 30cxi
GCN 47-047-24
F13 fault
PCB connection fault
if you are lucky it might just be a loose wire or connector on the PCB that needs reconnecting