Hi, 

Just a beginner question about GeoMason: when I want to use check points, I 
got the following:

java.io.NotSerializableException: 
com.vividsolutions.jts.index.quadtree.Quadtree
	- field (class "sim.field.geo.GeomVectorField", name: "spatialIndex", 
type: "class com.vividsolutions.jts.index.quadtree.Quadtree")
	- object (class "sim.field.geo.GeomVectorField", 
sim.field.geo.GeomVectorField@122a7b5)
	- field (class "sim.app.WebGalaSim.WebGalaSim", name: "junctions", 
type: "class sim.field.geo.GeomVectorField")
	- root object (class "sim.app.WebGalaSim.WebGalaSim", 
sim.app.WebGalaSim.WebGalaSim@1188793)
	at 
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)
	at 
java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
	at 
java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
	at 
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:141
6)
	at 
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
	at 
java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
	at 
java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
	at 
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:141
6)
	at 
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
	at 
java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
	at sim.engine.SimState.writeToCheckpoint(SimState.java:248)
	at sim.engine.SimState.writeToCheckpoint(SimState.java:261)
	at sim.app.WebGalaSim.WebGalaSim.main(WebGalaSim.java:199)


Is there a way to solve the problem? 

Thanks 

Francesco