I started using a new 910XT about 2 weeks ago. I'm on a Mac and using Garmin Express to sync data into Garmin Connect. I've noticed on a few occasions that my 910XT shuts off (e.g. physically powers down on its own) during data transfers. I haven't noticed a pattern, it's not really repeatable, and it doesn't happen every time. It happened again this morning as I was uploading today's run, so I thought I'd post to the forum to see if anyone has noticed this. Thanks!
Try leaving your heart rate monitor on. I think the input to the watch keeps it from shutting down. It's been working for me so far. Not a real fix but a good work-around.
krazyeone
It would make sense that the activity would be corrupt on the computer if the device powered down while it was transferring. If this were to occur, the activity would just need to be transferred again (by choosing Transfer all in the History menu). If the activity was corrupt on the watch, it is likely that this is actually what caused the device to power off, not the other way around. The activities are not modified on the watch during a sync.
Unfortunately, there is no logging options on the device since with an ANT device, we can't access the device memory to access any logs that would be created. However, we do have a case open for this issue since we have seen these reports in the forums. We have gathered the log files from Garmin Express when this occurs and are currently investigating the issue.
Jason