B4J Question Object reference not set to an instance of an object

Hi. Can someone tell me what the following error means when I open B4J ?

In English: Object reference not set to an instance of an object.




and here is the log file:

Build modules tree: 0
B4J version: 8.10
.Net version: 4.0.30319.42000
Ini folder: C:\Users\digro\AppData\Roaming\Anywhere Software\B4J
Build modules tree: 0
System.NullReferenceException: Object reference not set to an instance of an object.
en r.d(Object A_0, RoutedEventArgs A_1)
en System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
en System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
en System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
en System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
en System.Windows.BroadcastEventHelper.BroadcastEvent(DependencyObject root, RoutedEvent routedEvent)
en System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(Object root)
en MS.Internal.LoadedOrUnloadedOperation.DoWork()
en System.Windows.Media.MediaContext.FireLoadedPendingCallbacks()
en System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
en System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
en System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
en System.Windows.Media.MediaContext.Resize(ICompositionTarget resizedCompositionTarget)
en System.Windows.Interop.HwndTarget.OnResize()
en System.Windows.Interop.HwndTarget.HandleMessage(WindowMessage msg, IntPtr wparam, IntPtr lparam)
en System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
en MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
en MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
en System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
en System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
*** no reuse ***
Gui: 845
Build modules tree: 1
Gui: 555

Thanks for your help