Had the same problem and received this advice from a Whirpool tech and it's worked! Take the bottom rack out of dishwasher, then remove the round plastic filter and metal filter. You will see a small black, round plastic cover on the right hand side of this opened area. Do not remove as it is another valve filter but have a look to see if there is white gunk over it. If so, very GENTLY, with an old toothbrush and some warm water rub over the black filter to get rid of the gunk. Do not use anything else or be rough with it as it is quite fragile. After removing the gunk, put it all back together and try using again. You may have to hold the start button down again as the dishwasher could be out of cycle but it should work properly after that. Tech said if that doesnt fix it (it worked for me) you will definitely need to get a service call. Hope this helps...this tip saved me a service call and/or the cost of a new dishwasher.
Rosie, October 2010