Sounds like your door latch mechanism has failed, usually by two little bits of plastic breaking off. The latch holds the door closed and also switches the machine on - when it fails the on/off microswitch is stuck on hence the machine runs with the door open. Replacement parts readily available for about 12 to 15 pounds (google electrolux dishwasher door latch) and easy to fit - make sure you unplug before attempting a DIY repair or leave it to an expert. I just replaced mine by removing the outer door decor panel (6 screws with small torx head) and then the plastic panel along the top of the door with the switches on it (3 screws with small torx head). 2 Philips screws to undo the latch, two blade connectors (one's a piggy back connector to connect two wires)to swap over then re-assemble in reverse. DO NOT ATTEMPT WITH THE ELECTRICAL SUPPLY STILL CONNECTED - UNPLUG THE MACINE FIRST!!!
Peter
May 2009