What reason should you give for not transferring to another branch office with your firm?

I recently became engaged to an investment banker in New York. I asked the managing partner of my Boston firm about the possibilities of transferring to the New York office. He said not to worry, and set me up with the New York office for a round of interviews.

Unfortunately, the New York office will not hire me. I have not been given any reasons, either by the New York office of my firm, or from anyone in Boston.

The immediate fallout from this is that some of the partners in my own department have stopped giving me assignments, saying that they do not want to waste their time with me since my goal is to be in New York. A few partners insisted that I be kept on because my work is good. So, for the moment, I still have a job.