The Wisconsin Supreme Court, in the recent case of Bank Mutual v. S.J. Boyer Construction, Inc., et al, found that those who guaranty a note may remain liable on their guarantees, even when the lender releases the primary obligor in its quest to shorten the redemption period when foreclosing. The Supreme Court determined that when the statute says that all who are "personally liable for debt secured by the mortgage" are to be released, it means those on the note, and not those on the guarantee, which stems from a different obligation than the note.
So beware when signing guarantees: a lender seeking to get out from under an upside down mortgage may move with haste, releasing the primary obligors, shortening the period of redemption, and then seek full recovery from the guarantors!