Well, since everyone else is having issues with their aggravatin' characters, I thought I might share some of my pain with you all and let us commisserate together.
I write erotic romance. The stuff I write has a very definite sexual slant to it, and I am fond of using sex as character development--how a character grows sexually is a very important aspect of who that character is overall, and to gloss over that aspect is, I feel, a disservice to the character, especially when their sexual growth is a significant part of their character growth. So my books usually have a lot of sex in them--love scenes, sensual and sexual awareness playing a high-visibility role in the themes of the stories.
My current WIP, however, is causing some aggravation. My female lead suffers from amnesia along with severe cultural conditioning against sex. It takes a lot for her to even acknowledge that she has sexual feelings, much less actually engage with the hero. As a result, this current WIP isn't as chock-full o' nookie as I like to write 'em.
I don't think this will be a problem for my publisher, as they are great about accepting stories that are a little different. But that doesn't mean I don't still worry.
But sometimes the troublesome characters are the most fun to write. Having limits to what you can do with them means having to think creatively and think on your feet. For me as a writer, that lets me stretch my brain into new contortions--the kind that strike you at three AM and you wake up to a dark house thinking, "a-HA! Now I know how I'll get past that scene!" Even though your family is baffled by the dark circles under your eyes the next morning.
Man, I love this job!