It worked perfectly all year. We went on a ski vacation during the week before Christmas and were gone for five days, during which time the dishwasher was not used. When we got back, it started leaving specks of dirt or food or whatever on some of the dishes. This condition seems to be getting worse. I can't see why a week of inactivity would cause this but this is the only time we were away for an extended period of time and the problem started when we returned.
The user's manual suggests scraping the dishes before putting them into the dishwasher and loading properly when this happens. We do both and are doing nothing different than we were doing all year.
Before calling a repairman, I suggested that my wife run a cycle with no dishes in in to clear out the lines, then to run a small load to see what happens. She's doing that today. Any other suggestions as to what might be causing this?