Yup. I've had that blank stare interview. I've decided that the next time it happens, I'm going to attempt to patiently explain to the interviewer why that isn't going to get them the information they want. Last time it happened I was hired anyway because this was only one interview of many. It turns out the bad interviewer was a nice chap and very clever, but with no understanding of how humans work. I've found that such people are often interested to know why their interactions are failing. They want to learn new rules that they can add to the personality simulator they run in their head :-)