Cec Murphy is running a series on editors. It would be worth the hop over there to read all the posts.
This hasn’t happened to me (yet), but it’s not uncommon among authors. You might as well prepare yourself in case it happens. So here are a few tips for responding to the request for a serious revision.* Respect your editor and her opinion. It’s easy to tell yourself your editor wants to ruin your marvelous writing. Or you can tell yourself that you’re a good writer—and that person is only an editor and he doesn’t know good writing. Read more.