Hello, Did you manage to get this sorted? My phone has just done this today, it's driving me mad. I have a Samsung Galaxy S3. Thanks
I went to the dealer's service, they made a hard reset with the computer. It was fixed for one day! I think there is a problem with sync connection when the phone restarts unexpectedly, it crashes... I changed phone for sync use because with the HTC was no hope. No problems at the moment.