With the new and not-improved appliances that are supposed to be energy saving comes a slew of other problems. The new washers do not seem to fill with water over 80 degrees (cold) even when a hot wash is selected. This causes buildup of bacteria, mold and gunk. The manufacturer solution is to purchase Affresh to clean the washer once a month ($12 for six tablets) on mine it specifically shows a setting for Affresh clean. Rather than going to the extra cost there are a couple of other solutions. A cup of bleach is also suggested in the manual for my Whirlpool Roper but you don't want to use the Affresh cleaning cycle but instead a regular wash.
Another suggestion is to use vinegar and baking soda.
Take a look at DIY Natural for instructions.