Lets see.
Reason #1: The first wife was sleeping with the neighbor.
Reason #2: The second wife was sleeping with her boss.
Solution #1: That's what shotguns are for (see Salem's Lot)
Solution #2: That's what staplers are for (you know, those heavy-duty H&R Block type staples)
Seriously... I'm sorry man (and to all you guys that have had problems like this). I can honestly say that I have no idea how I'd react to something like that... and I don't think any of us do until we've actually walked in those shoes. I hope and pray that I never have to.
Honestly, I went through that as well, and as odd as this sounds, I got over it pretty quick. My ex cheated three times that I know of; the first was an allegedly "platonic, spiritual friend" and while I had no actual proof of the consummation, and therefore didn't leave, the hurt and anger kind of wore off with that one, so that when I was on a long term assignment for work, and only home for the weekends, and the second happened, I kind of didn't care. Just don't embarrass me or spend my money on him. I finally drew the line when the latter happened. She said she was sorry and "wanted to recommit" and would put in the effort with me. It lasted about three months and on to number three, and by that time the prevailing emotion was "relief". I never slept with anyone else while married, but I would go out and have fun at bars in the city and perhaps did a few things I wouldn't have done if I was really in love or if I cared about the consequences (or her feelings).
It is what it is.