Sounds like there might be a problem with your door switch or your door switch not being activated when you shut the door. Check the catch that goes into the switch isn't broken, also check the two screws that hold the switch in place are tight (these are accessed from outside the machine two screws that are visible when the door is open) if they are ok then probably your switch is faulty. This is not difficult to check but means removing the front cover (which should always be done with machine switched off & plug pulled out) & only if you feel confident enough to do it
Graham
May 2006