A bit more detail...
*** EXCEPTION ***
System.InvalidOperationException: This Visual is not connected to a PresentationSource.
at System.Windows.Media.Visual.PointFromScreen(Point point)
at #g7i.#I9i.#y8i(Point #bVe)
at ActiproSoftware.Windows.Controls.Docking.Logic.WindowDragProcessorBase.#cNi(Point #bVe)
at ActiproSoftware.Windows.Controls.Docking.DockSite.NotifyWindowDragMove(Point location)
at #g7i.#B9i.#d8i(Object #xhb, EventArgs #yhb)
at System.Windows.Window.OnLocationChanged(EventArgs e)
at System.Windows.Window.WmMoveChangedHelper()
at System.Windows.Window.WmMoveChanged()
at System.Windows.Window.WindowFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.PublicHooksFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
Tue Apr 05 2016 19:41:11.7716 [TRACE] TID: 9 Showing exception dialog: This Visual is not connected to a PresentationSource.