if the card becomes corrupted either on its own or by the unit itself, it can lock up the unit and changing the card often fixes the issue. i advise this since its simple and easy to do and since you are a distance away from your network it might save you a trip or the hassle of sending it in for warranty evaluation . Speaking from experience , reformatting does work sometimes but there are times that a card cant be used since it continually causes issues. I prefer 16gb sandisk in mine but nay quality class 10 card should work.