I have had cracks fixed on my Martin D35 and Larrivee parlor guitar. The luthier that fixed them said the most common cause is low humidity that Clinton mentioned earlier.

Its not much of a job for a good luthier to fix. The procedure used on my guitars was to put them in a moist environment. This will cause the crack to practically disappear. Glue is then forced in the crack and a couple small diamond shaped wedges are placed near each end of the crack on the inside of the guitar. When finished it wasn't possible to tell where the cracks were located.    The cost will most likely be considerably less than the cost of shipping the guitar somewhere.

During the winter the humidity can become quite low especially in the north with forced air heat. I ended up buying a meter to measure humidity and two humidifiers.   

Cap't Bob