Leakage in attic after wind-driven rain.
 Possible cause: Leaky or inadequate shingle underlayment or deteriorated flashing

Ice forms in the gutter and works its way under the shingle pushing the shingle up to the wind. Upon melting it leaks into the home.

Stains on interior ceilings and walls or mold and mildew growth Possible cause: Inadequate or faulty shingle underlayment allowing leakage or inadequate ventilation