Removed the Material Boundary option from the edge detection options in

the Parameter Editor mode.  The Material Boundary toggle button takes
effect only in the Python Scripting mode.  Instead the Parameter Editor
mode automatically determines which edge types need to be computed on the
basis of user-specified line selection criteria in terms of edge types.

Problem report from Light BWK through personal communications, thanks!

release/scripts/startup/bl_ui/properties_freestyle.py

@@ -138,7 +138,8 @@ class RENDERLAYER_PT_freestyle(RenderLayerFreestyleButtonsPanel, Panel):
         
         col = split.column()
         col.prop(freestyle, "use_smoothness")
-        col.prop(freestyle, "use_material_boundaries")
+        if freestyle.mode == 'SCRIPT':
+            col.prop(freestyle, "use_material_boundaries")
         
         # Advanced options are hidden by default to warn new users
         if freestyle.use_advanced_options: