I had a similar thing happen to me yesterday when calling my insurance company. They asked for my secret security code before they would continue talking to me. I was just totally blank! I started to just spit out all of the passwords that I knew of and she finally said, "your mother's maiden name?"
I was so flustered by then I gave her my MIL's mother's maiden name, my wife's maiden name and then stopped and asked her who's maiden name did you need again? She then asked me for MY mother's maiden name. Yes, I knew that but couldn't remember right off what it was.
After about 30 seconds of stumbling around it finally came to me and I gave it to her. I then asked if there was anything else? She said, "no, that was quite enough." Then we did our business. Thank goodness they are so patient. Great customer service.