I just found and (I believe) fixed a race condition in SparseGrid2D, SparseGrid3D, Continuous2D, and Continuous3D which can cause certain methods to perform incorrectly when using multiple threads.  If your code is single-threaded (you're not using ParallelSequence), or you're not using the methods listed below, there's no problem.

Affected Sparse Grid methods: getObjectsAtLocation, numObjectsAtLocation, removeObjectsAtLocation 

Affected Continuous methods: getNearestNeighbors

If you just want the updated jar file, you can get it here:
	http://cs.gmu.edu/~sean/temp/mason.17.jar

Sean