Each time I start a new map it allows me to save a few times and updates the map. Then after about 15 minutes of using the program I get a message saying that the map was not saved and when I try and re-open the file it says the file cannot be opened. With all of these maps I have inserted a JPEG file of a map of the World of Greyhawk someone else made and began re-working it. Why is this happening? What can I do to prevent it.