Problem with a Miele 'Novotronic Premier Plus' washing machine cutting out?

Our machine cuts out during a wash cycle after running for not very long.
It will do other things like rinse or spin without a problem.
During the wash cycle, it runs for a few minutes then cuts out (popping the main breaker on the domestic unit).
I am guessing that this occurs at the time when the water heater would be starting. I have tested the heater in situ with an avo meter and I can find no leaks to earth from any of its terminals.
The inside of the machine looks very clean with no signs of water leaks at all.
This problem occured before a few months ago and we did not use the machine for a couple of weeks. When I got round to having a look at it we ran the wash cycle to be double sure when the problem occurred. Suprisingly it worked ok! It has continued to work ok until last week. We guessed at the time that perhaps there was some damp inside which has dried up, thus causing it to work again. Looking inside it now, with no sign of any dampness that theory would appear to be wrong. Now it continues to go wrong.
Can anybody help please?
John Fletcher. email: johnf@warmweb.co.uk