K.N.
I am aware of products called "brown sugar softeners" (little pottery pieces that you soak in water and then place in hardened sugar, dried fruit, etc.). They usually cost a few dollars:
http://www.amazon.com/Brown-Sugar-Softener-Maple-Leaf/dp/...
http://www.seefred.com/cgi-bin/shop.pl/page=brownsugarbea...
You can also try placing the "sugar" in a plastic bag and add an apple wedge; allow it to remain in the bag for a day or two until the sugar softens. Then use a blender or food processor to better break up the hardened sugar granules.