I always go into interviews with a few of these "negative" types of stories prepared with the most positive spin possible. never make it anything too big of a deal, but it shouldn't be without issue either. and always discuss what you learned from it or how you've changed. In other words, when the interviewer is looking for a negative answer or an opportunity it should really be that with a positive spin, not something that's really a positive that you've spun negative (I work too hard, I'm a perfectionist, etc. - make it more like I need to work on my public speaking skills and I've joined XYZ group to help me with that or I should have been more open with my concerns earlier in the process as it would have saved time and frustration.) This is a classic MBA interview technique. I saw it alot.