Re: clothes washer backup!
What is the height of the stand pipe in relation to the top of the washer? The stand pipe is where your washer hose is inserted and it should be at or above the height of the washer. I agree with Canuk that your problem could be indicative of an improperly plumbed system, only exploratory surgery will ferret that out, but you don't have to go all Chuck Norris on it. You can carefully cut the drywall out of the stud bay that the supply and discharge lines are in. If you are careful about it, you may be able to save the piece you remove and reuse it.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!