Call me unprepared, but I wasn't aware interviews were even a potential part of the process. I applied having worked in industry for 6 years, and am a little out of touch. I think that was obvious in the interviews, actually - my question was basically "I have no idea how this works, I'm out of touch, how do you even". I had an interview with Berkeley and MIT. The professors in both cases asked similar questions, but I felt one interview went quite well and the other very much did not. It was enlightening and tragic.
I'm mostly posting because:
This actually happened in my Berkeley interview. Twice. I was in Canberra, Australia and it was a 40 C day, so the router at home kept having a fit. In the end the professor just called me on my mobile and we completed the interview over the phone. The next day I put a fan next to the router. But I was made an offer, so it didn't matter in the end. That's not something you need to worry about!