How do you answer this interview question?

Can anyone give me an example of how or what is it that an prospecitive employer wants when they ask for a situation where you blew it with a patient and how you handled it? This question really throws me and I just don't know what they are wanting.
My best guess is that they're trying to see if you're willing to own up to your mistakes and how you deal with them. Did you show professionalism and maturity or did you over react or fall apart? Were you able to rectify the situation to the patient's satisfaction? What did you learn from that experience about how to handle things in the future when everything just plain falls apart?

Also, I think the question is meant to throw you off balance and see how well you recover.

if your response includes excuses it shows a lack of accountability.

Ditto to all of the above. Come up with an answer to this one as you might expect to hear it again or something similar.