In case where homeowner in construction defect case obtained a default judgment against the contractor then brought action against the contractor's insurer for payment on the default judgment, summary judgment for insurer is reversed as: 1) where a default judgment results from a lack of notice by the insured, the insurer is liable on the judgment unless it suffered actual, substantial prejudice; and 2) the mere inability to investigate the claim thoroughly or to present a defense in the underlying suit does not satisfy the prejudice requirement.