The new Anglican ordinates and the question of divorce
Divorce is a sticky subject in the Catholic Church. The recent moves to allow certain Anglicans into communion with Roman in their own "Ordinates" will certainly make the issue more complicated.
In prior years, divorce in the Church was considered forbidden - however nowadays, it is not divorce which is sinful, it is remarriage until after the original marriage is annulled. The cynical would say that annullments are big business in the Church and they certainly complicate things when the Catholic party gets an annulment while a Protestant spouse who is divorced does not (and occassionaly the parish priest blessing the union after the fact looks the other way).
When one partner is abusive or alcoholic, it is obvious that this partner was incapable of forming or maintaining a marriage bond - even if this was not apparent when the marriage was made (often because alcoholism and abuse are related and middle or late stage alcoholism is not always apparent on the wedding day). An annulment in such cases is usually not complicated.
In the ancient Church, if someone was married to a pagan and converted, they could get married again in the Church for the very sound reason that staying married to a pagan would involve apostacy when the family made offerings to the pagan spouses deity or celebrated pagan feasts (in the days before the Church began coopting such events).
When the Reformation happenned, many Protestant sects read the scripture on divorce where it referred to immorality as adultery - although the Catholic Church has never endorsed this view. I can see the logic behind this, since this would seem to allow someone to cheat and then put away his or her spouse scott-free. This is hardly just to the wronged spouse.
Adultery, as the word is defined, is not about adulthood but the adulteration of the marriage. It was originally considered a property crime to be punished by death (as all such crimes were, but are no longer). Jesus teaching on divorce was actually meant to level the playing field between the sexes, since males could put away their wives but wives could not put away their husbands. Jesus solution was to restrict husbands from easy divorce. This lesson has not been learned in other monotheistic sects, where the man is still priviledged in divorce in Islam and some Orthodox Jewish sects (where the husband can object to the Gett disolving the marriage).
Once a marriage is adulterated, is this not the same thing as saying that it has been ended? Perhaps the answer to the question of adultery in divorce is to recognize the absolute right of the wronged party to decide if the marriage is to endure, while the adulterous party has no such right to resist their decision (and indeed would always have an impediment to marriage with the party with whom the adultery was committed). This seems entirely reasonable, especially given the meaning of the word adultery and the intention of Christ's teaching to level the marital playing field - raising women to equality from their status of property. While it is certainly virtuous to forgive a cheating spouse, it should not be required - especially if the cheating spouse is unrepentent.