Index: /issm/trunk-jpl/src/m/classes/stressbalance.py
===================================================================
--- /issm/trunk-jpl/src/m/classes/stressbalance.py	(revision 20279)
+++ /issm/trunk-jpl/src/m/classes/stressbalance.py	(revision 20280)
@@ -195,7 +195,14 @@
 		WriteData(fid,'object',self,'class','stressbalance','fieldname','referential','format','DoubleMat','mattype',1)
 
-		WriteData(fid,'data',self.loadingforce[:,0],'format','DoubleMat','mattype',1,'enum',LoadingforceXEnum())
-		WriteData(fid,'data',self.loadingforce[:,1],'format','DoubleMat','mattype',1,'enum',LoadingforceYEnum())
-		WriteData(fid,'data',self.loadingforce[:,2],'format','DoubleMat','mattype',1,'enum',LoadingforceZEnum())
+		if numpy.isnan(self.loadingforce):
+			lx=float('NaN'); ly=float('NaN'); lz=float('NaN');
+		else:
+			lx=self.loadingforce[:,0];
+			ly=self.loadingforce[:,1];
+			lz=self.loadingforce[:,2];
+
+		WriteData(fid,'data',lx,'format','DoubleMat','mattype',1,'enum',LoadingforceXEnum())
+		WriteData(fid,'data',ly,'format','DoubleMat','mattype',1,'enum',LoadingforceYEnum())
+		WriteData(fid,'data',lz,'format','DoubleMat','mattype',1,'enum',LoadingforceZEnum())
 
 		#process requested outputs