We are not aware of this problem with blurred settings pane.
So in order to investigate the problem is it possible to give us some additional information, like:
What is the version of our controls/demo used?
What browser and its exact version you are using?
What is the version of the Silverlight plug-in used?
What is the Operating System and the version of the .NET framework installed?
As for undoing the text of a node or edge in the MindMap example - this is not possible out of the box.
The text in a node (or edge) in the MindMap example is not a property of a RadDiagramShape (RadDiagramConnection) and therefore its change is not recorded in the Undo/Redo service. In the MindMap example this text comes from the business property (the ViewModel) and are not native property of the RadDiagramShape (RadDiagramShape) control.
All the best,
the Telerik team