Hiya honey.
This once happened to me. First remove the waste pipe from under the sink, then lower it into a bowl or something. This will drain any water away that's in the washing machine. Make sure this pipe is low to the ground near the washer as well, otherwise it won't drain. Once your satisfied there isn't any water in, take a normal cutlery knife or something with a blunt end, then put it where the door lock is. If you wiggle it around there at an angle whilst pulling forward the handle to open the washer, it will come open.
I learnt this off my brother who is a plumber years ago and it's never failed. I've even passed it onto my friends and they've managed to do this as well.
If you don't understand what I mean - let me know.
Good luck!!
Janet Hara, February 2009