This is usually the result of the power or the water supply to the machine being interrupted. Ensure that the water and power are back on and continue with the cycle. If this keeps happening then an electrician or plumber should be able to help.
It is also worth checking that nothing in the dishwasher is pushing against the door. If the door opens even slightly then the programme will stop immediately. Ensure the door is closed firmly and that the latch is fully engaged.