I too have that problem sometimes

Quote Originally Posted by Catty1
Vinegar too!

Or soak them in hot soapy water with bleach for 1/2 hr or so.

(PS - you can use vinegar - I'd say a cup or a bit less - for the next two washes and every so often after that. Helps de-scale the wee pipes too.)
Do you put the vinegar in with the dishes, or run it empty for a cycle?