The machine will have tiny bits of food debris sloshing around in it - quite normal - when the dishes are finally rinsed droplets of water may remain on them with bits of crud in the droplets. The drying cycle bakes the droplets and the debris remains stuck to the crocks. To stop this happening Rinse Aid is injected into the rinse water to break down surface tension and allow the water to drain off in sheets rather than droplets.
Use a good quality Rinse Aid and keep it topped up.
Make sure you always put dishwasher salt in when the machine asks for it.
Scrape off the worst of the debris before loading the dishes.
Load the machine so that all of the dishes get splashed properly.
Good luck...
Peccavi
February 2010