I liked your post musicgirl... On another message board I was on, they would say that there are only two Biblical reasons, but wouldn't go into why or whatever.
I hope that I don't marry a non-believer, a cheater or an abuser, but those things do happen and I hope that I will try my very hardest to make the marriage work in those circumstances if they ever came up, but I can't say right now how successful I'd be.
I heard someone say once something about an abusive spouse was obviously not a Godly one and so that would be okay under the non-believer divorce category. I know you can't judge someone's heart about whether they're right with God or whatever, but I sort of agree with that to an extent. A Godly man would not abuse his wife.
I hope I don't marry someone who is abusive, but if I do and they don't work with me to work it out and get help and they keep doing what they're doing, I would get a divorce for myself and especially for the children (if there were any).
I'm not against remarriage, but people should just be careful (actually they should have been careful the first time around :-P)