This happened to me this morning. I was trying to stop down and the dial moved, but nothing happened. Yes, Life can send us nasty experiences. I was fortunate I was just shooting a house exterior and not THE KISS at a wedding. (Good reason to have an assistant backing you up?)
I did the battery thing and all went quite well thereafter. I just did the 1.2.3 firmware update; I’m not necessarily making any connection beyond coincidence, but if it happens again soon, I will check into that possibility.