Exactly the same thing happened to me, I rode my bike to work and when I arrived it had broken in exactly the same place. Must be a weak point on the watch as it had no impact at all. Did anyone get an answer from garmin?
I got a reply from Garmin when I contacted them directly, asking me to send a receipt. I only bought the watch (Brand New) a year before that via eBay! Didn't hear a thing after that!