
Does the stacktrace help you isolate the problem?
An exception of type 'System.InvalidOperationException' occurred in PresentationFramework.dll but was not handled in user code
Specified element is already the logical child of another element. Disconnect it first.
bei System.Windows.FrameworkElement.ChangeLogicalParent(DependencyObject newParent)
bei System.Windows.FrameworkElement.AddLogicalChild(Object child)
bei ActiproSoftware.Windows.Controls.Docking.Primitives.DockingWindowContainerBase.woM(Object , NotifyCollectionChangedEventArgs )
bei System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
bei System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)
bei ActiproSoftware.Windows.Controls.Docking.Serialization.DockSiteLayoutSerializer.gvS(DockSite , XmlDockSiteLayout , DockHost , XmlToolWindowContainer , DockingWindowState )
bei ActiproSoftware.Windows.Controls.Docking.Serialization.DockSiteLayoutSerializer.Jvn(DockSite , XmlDockSiteLayout , XmlRaftingHost , DateTime )
bei ActiproSoftware.Windows.Controls.Docking.Serialization.DockSiteLayoutSerializer.OvG(DockSite , XmlDockSiteLayout )
bei ActiproSoftware.Windows.Controls.Docking.Serialization.DockSiteLayoutSerializer.ApplyTo(DockSite obj)