Did you forget to remove the clothes after a wash cycle?
Never fear - you won't have to throw them all out!! Just start the washer for another cycle but this time instead of using any detergent or fabric softener, use a cup of plain white vinegar. Nothing else. Let the wash/rinse cycle finish and your clothes should not have any musty or mildewy odor. The vinegar scent will probably make you wrinkle your nose but believe me, it doesn't hang around. If it worries you, do one more cycle with your regular detergent and fabric softener. But this time remember to remove the clothes from the washer at the end of the cycle!