I have just started experiencing this problem and so far haven't been able to find a solution. it worked fine two days ago and earlier today when I replaced the batteries in my speed and cadence sensor. it turned on fine and found the sensors in seconds. I turned it off and then half an hour later when I needed it I found it would only stay on for 5 seconds before turning it's self off. my computer doesn't show it connected so I can't do anything with it. someone please help. I have also had several messages saying the memory is full when it isn't. also the device won't turn off when plugged in to show the charge screen, even though it was on 96%. when plugged in the device also won't load beyond the start up page with the garmin logo, it won't load maps or go any further.