We also have a similar problem on our Ferroli Optima 1001
Intermittent, but now needs resetting several time per day on either hot water or Central heating. Engineer has replaced thermistors, checked gas flow, but we still have the problem.
It 'may' be the board, but this will cost us £260 to find out whether this is the problem and thats almost 1/4 cost of a new boiler :)
Dave, November 2009