Right in the middle of the job. The capacitor stopped charging, and the ready light would not come on, and no matter what freshly charged batteries I stuck in there it still said "batt". I looked it up, and there is a circuit that goes bad, and a new module needs to be put in. So this is pretty much exactly what I was so afraid of, and it happened. It was like a bad dream. I tried not to panic, but it was one of the single most stressful events in my recent memory. I had to finish the whole reception with my on-board flash, and the photos LOOK LIKE SHIT. I felt so bad about it I wanted to cry. At least I got the ceremony, and all of her wedding party photos. I will never do another wedding again without a backup flash. Not that I will ever be able to afford one. So it goes. I feel like a tool.
Anyway, now I have no speedlight for however long it takes Nikon to fix it and send it back. Where did I put that warranty card?