Lack of rinse aid (liquid rinse aid) often causes this.
The rinse aid encourages the rinsing water (with bits in it) to drain off in sheets rather than to form droplets which just get baked on hard.
The debris on the crockery will be small bits of food and calcium deposits from hard water so you should ideally feed the machine with Salt & Rinse Aid as well as detergent.
Good luck...
Peccavi
March 2013