this is due to 2-1, 3-1,4-1 tabs.
give the machine a run through with an empty load 4-5 times then revert back to using powder as this breaks down easier than tabs and does not leave such a large residue in your machine which causes the heating element to corode.
belive it or not about 90% of dishwashers are not designed to take tabs.
paul robinson, May 2007