Have you tried bleach? Apply with a rag or sponge dampened with hot water, let it sit a few minutes and then rinse well with warm water. That should kill the mildew that causes the odor.
Or you could probably do the same by running a load of whites in hot water using bleach.
If you don't like bleach, white vinegar will do about the same. You may need to run a straight water cycle to clear out the vinegar smell, though.
