I had this problem and I discovered that it was as a result of the cutlery basket shedding a few bits of plastic which got into the works and which blocked the outlet pump mechanism. This happened a couple of years back but I seem to remember that I took off the lid which allowed me to remove the left hand panel. This revealed amongst other things a double plastic reservoir. This reservoir was easy to remove as it has push fit joints and it made it easy to flush it through. I also threw away the old cutlery basket!
Peter H, November 2008