Business Insider:

On yesterday's Fox News Sunday, Chris Wallace asked guest Michele Bachmann whether "she was a flake."

“The rap on you in Washington is that you have a history of questionable statements, some would say gaffes,...are you a flake?”

Responded a calm but frustrated-looking Bachmann: "Well I think that would be insulting to say something like that, because I’m a serious person.”

Here's the clip of the full interview (which does cover a lot of substantive ground).  The "flake" part enters in the 14th minute:

Shortly after the pre-taped interview aired on Fox News Sunday, Chris Wallace posted his regular, post-show "Wallace Unplugged" video. In it, he apologized for the question noting that many viewers were "more than perturbed" by the phrasing: "And since in the end it’s really all about the answers and not about the questions. I messed up, I’m sorry. I didn’t mean any disrespect.”

However, Bachmann doesn't seem to be overly impressed with the apology at this point. Politico:

Via POLITICO's Jennifer Epstein, Michele Bachmann isn't accepting an apology from Fox News Sunday host Chris Wallace for asking her yesterday, "Are you a flake?"

ABC News' Jon Karl, who's been getting face-time with Bachmann in Waterloo in advance of her formal campaign announcement, played a clip of the web video in which Wallace said, "I messed up. I'm sorry."

When Karl asked if she accepts the apology, Bachmann brushed aside the question this way: "I think that it's insulting to insinuate that a candidate for president is less than serious."

Trying the question again, Bachmann replied, "Those are the small issues. I'm focused on the big ones."