You are experiencing the error below when trying to change the EndPopint a link to the same ShapeNode.

------------------------------------------------------------
Error:

Microsoft JScript runtime error: Unhandled Error in Silverlight 2 Application
Code: 4004   
Category: ManagedRuntimeError      
Message: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
   at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
   at System.ThrowHelper.ThrowArgumentOutOfRangeException()
   at System.Collections.Generic.List`1.get_Item(Int32 index)
   at MindFusion.Diagramming.Silverlight.DiagramLink.xf422031a8b306720(Int32 xe24dd90acb923d68)
   at MindFusion.Diagramming.Silverlight.DiagramLink.x4cf22ee19af1c11d(Point x3bd62873fafa6252, InteractionState xab29833053004740)
   at MindFusion.Diagramming.Silverlight.DiagramLink.EndDrag(InteractionState ist)
   at MindFusion.Diagramming.Silverlight.InteractionState.Commit(Point currentPoint)
   at MindFusion.Diagramming.Silverlight.BehaviorBase.OnMouseUp(MouseButtonEventArgs e)
   at MindFusion.Diagramming.Silverlight.Diagram.x66c89b500bffc63d(Object xe0292b9ed559da7d, MouseButtonEventArgs xfbf34718e704c6bc)
   at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)    



------------------------------------------------------------
Steps to reproduce the problem:

1 - Setting the record:

            diag.AdjustmentHandlesSize = 12;
            diag.AllowInplaceEdit = false;

            diag.HitTestPriority = HitTestPriority.ZOrder;

            diag.AllowMultipleResize = true;
            diag.LinkStyle = LinkStyle.Cascading;
            diag.LinkSegments = 3;

            diag.AlignToGrid = false;
            diag.GridColor = Colors.Green;
            diag.AllowUnconnectedLinks = true;
            diag.RouteLinks = true;
            diag.RoutingOptions.GridSize = 15;
            diag.RoutingOptions.Anchoring = Anchoring.Keep, / / Ignore
            diag.RoutingOptions.CrossingCost = 20, / / 4
            diag.RoutingOptions.DontOptimizeLongRoutes = false, / / false
            diag.RoutingOptions.EndOrientation = MindFusion.Diagramming.Silverlight.Orientation.Auto; / Auto
            diag.RoutingOptions.LengthCost = 4, / / 2
            diag.RoutingOptions.NodeVicinityCost = 5, / / 2
            diag.RoutingOptions.SmartPolylineEnds = true, / / true
            diag.RoutingOptions.StartOrientation = MindFusion.Diagramming.Silverlight.Orientation.Auto; / Auto
            diag.RoutingOptions.TriggerRerouting = RerouteLinks.WhenModified; / / WhenModified
            diag.ShapeBrush = new SolidColorBrush (Color.FromArgb (205, 173, 255, 50));
            diag.DynamicLinks = false;
            diag.ShowAnchors = ShowAnchors.Auto;
            diag.ZoomFactor = 100;
            / / ===================================== ========== Selection ===========================
            diag.Selection.AllowMultipleSelection = true;
            diag.Selection.Pen.Brush = Speed.Windows.Brushes.Blue;
            diag.Selection.Pen.Thickness = 4;


2 - Create 2 ShapeNodes
3 - Create a link between ShapeNodes
4 - Select the Diagramlink
5 - Change the endpoint of the link several times in the same ShapeNode
6 - This error is intermittent. Generally works, but sometimes the error occurs above