On my way to work, on a dark and drizzly morning, I hit a new, but nasty pothole, while doing about 90 kph. All seemed fine until I got close to work, where at the slower speed and shifting gears, I noticed a scary clunking noise. It turned out that my chain had become slack. I know it was fine, before the incident, because I'm anal when it comes to doing the pre-ride inspections. The pinch bolt was found to be quite secure, when I readjusted the chain. After it was adjusted, everything was good on the return trip. Has anyone every heard of this happening before?