One word is all you need to remember: REFRAMING...
Step 1: Repeat the question, check you've understood tight (you know most people like the sound of their own voices, they sometimes let you off the hook by just carrying on talking...:-)
Step 2: If it's still up to you, then reframe the question: go back in time, how did we get into this position ? what are the real issues at stake ? what did we both want out of this situation in the first place ? what's changed since then ? then you can say: so perhaps the real question is.....and ask it in its new shape.
At least then it's a question you'll be happier to answer.