Mine was doing that for awhile. It seemed like the main sweep hand was jammed or something. If I started the stopwatch, it wouldn't move, and when I stopped the stopwatch and reset it, the main sweep hand would just vibrate. I had the battery replaced, and it stopped for awhile but came back. I was going to send it in to Oakley and stopped wearing it for a few days, but it started working fine again, so I'm not sending it in right now...