I was using version 3.5 and updated to 4.5.22477.12540 and now I have this null exception when deseserializing  my layout.

Call Stack

   at Xceed.Wpf.AvalonDock.Layout.LayoutContent.UpdateContainedFloatingWindowTaskbarTitle(Boolean newValue)

   at Xceed.Wpf.AvalonDock.Layout.LayoutContent.OnIsSelectedChanged(Boolean oldValue, Boolean newValue)

   at Xceed.Wpf.AvalonDock.Layout.LayoutContent.set_IsSelected(Boolean value)

   at Xceed.Wpf.AvalonDock.Layout.LayoutContent.OnParentChanging(ILayoutContainer oldValue, ILayoutContainer newValue)

   at Xceed.Wpf.AvalonDock.Layout.LayoutElement.set_Parent(ILayoutContainer value)

   at Xceed.Wpf.AvalonDock.Layout.LayoutGroup`1._children_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)

   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)

   at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)

   at System.Collections.ObjectModel.Collection`1.Remove(T item)

   at Xceed.Wpf.AvalonDock.Layout.LayoutRoot._hiddenAnchorables_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)

   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)

   at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)

   at Xceed.Wpf.AvalonDock.Layout.LayoutAnchorable.Hide(Boolean cancelable)

   at Xceed.Wpf.AvalonDock.Layout.Serialization.LayoutSerializer.FixupLayout(LayoutRoot layout)

   at Xceed.Wpf.AvalonDock.Layout.Serialization.XmlLayoutSerializer.Deserialize(TextReader reader)

   at Wtvision.R3SpaceDesignerWPF.MainWindow.LoadLayout(String layoutName) in D:\GVV\Graphics\Applications\R3SpaceDesigner\master\R3SpaceDesigner.xaml.cs:line 2646