have you cleaned the filter internally? I had the same problem for ages until I realised you have to pull forward the little door at the front, unlock the filter there, pull it out the large internal filter (careful as you get excess water on the floor) and then rinse it under the tap to get all the stuff out of the filter. Then mine worked perfectly. Sorry if you have already done this, it just took me a while to work out that cleaning the filter was not just wiping down the internal door and the front tray!
mrs L, January 2011