I have same problem. Windows log message:

Aplikacja: Plan-G3.exe
Wersja architektury: v4.0.30319
Opis: proces został przerwany z powodu nieobsłużonego wyjątku.
Informacje o wyjątku: System.ArgumentException
Stos:
   w MS.Internal.AppModel.ShellUtil.GetShellItemForPath(System.String)
   w Microsoft.Win32.FileDialog.PrepareVistaDialog(MS.Internal.AppModel.IFileDialog)
   w Microsoft.Win32.FileDialog.RunVistaDialog(IntPtr)
   w Microsoft.Win32.FileDialog.RunDialog(IntPtr)
   w Microsoft.Win32.CommonDialog.ShowDialog()
   w Plan_G3.MainWindow.<.ctor>b__3(GalaSoft.MvvmLight.Messaging.NotificationMessageAction`1<System.String>)
   w GalaSoft.MvvmLight.Helpers.WeakAction`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Execute(System.__Canon)
   w GalaSoft.MvvmLight.Helpers.WeakAction`1[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].ExecuteWithObject(System.Object)
   w GalaSoft.MvvmLight.Messaging.Messenger.SendToList[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](System.__Canon, System.Collections.Generic.IEnumerable`1<WeakActionAndToken>, System.Type, System.Object)
   w GalaSoft.MvvmLight.Messaging.Messenger.SendToTargetOrType[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](System.__Canon, System.Type, System.Object)
   w GalaSoft.MvvmLight.Messaging.Messenger.Send[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](System.__Canon)
   w Plan_G3.ViewModel.MainViewModel.OpenFlightPlan_Executed(Plan_G3.Model.FlightPlanFileType)
   w Plan_G3.ViewModel.MainViewModel.<.ctor>b__2c()
   w GalaSoft.MvvmLight.Command.RelayCommand.Execute(System.Object)
   w MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(System.Windows.Input.ICommandSource, Boolean)
   w System.Windows.Controls.Primitives.ButtonBase.OnClick()
   w System.Windows.Controls.Button.OnClick()
   w Fluent.Button.OnClick()
   w System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(System.Windows.Input.MouseButtonEventArgs)
   w System.Windows.UIElement.OnMouseLeftButtonUpThunk(System.Object, System.Windows.Input.MouseButtonEventArgs)
   w System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(System.Delegate, System.Object)
   w System.Windows.RoutedEventArgs.InvokeHandler(System.Delegate, System.Object)
   w System.Windows.RoutedEventHandlerInfo.InvokeHandler(System.Object, System.Windows.RoutedEventArgs)
   w System.Windows.EventRoute.InvokeHandlersImpl(System.Object, System.Windows.RoutedEventArgs, Boolean)
   w System.Windows.UIElement.ReRaiseEventAs(System.Windows.DependencyObject, System.Windows.RoutedEventArgs, System.Windows.RoutedEvent)
   w System.Windows.UIElement.OnMouseUpThunk(System.Object, System.Windows.Input.MouseButtonEventArgs)
   w System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(System.Delegate, System.Object)
   w System.Windows.RoutedEventArgs.InvokeHandler(System.Delegate, System.Object)
   w System.Windows.RoutedEventHandlerInfo.InvokeHandler(System.Object, System.Windows.RoutedEventArgs)
   w System.Windows.EventRoute.InvokeHandlersImpl(System.Object, System.Windows.RoutedEventArgs, Boolean)
   w System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject, System.Windows.RoutedEventArgs)
   w System.Windows.UIElement.RaiseTrustedEvent(System.Windows.RoutedEventArgs)
   w System.Windows.UIElement.RaiseEvent(System.Windows.RoutedEventArgs, Boolean)
   w System.Windows.Input.InputManager.ProcessStagingArea()
   w System.Windows.Input.InputManager.ProcessInput(System.Windows.Input.InputEventArgs)
   w System.Windows.Input.InputProviderSite.ReportInput(System.Windows.Input.InputReport)
   w System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr, System.Windows.Input.InputMode, Int32, System.Windows.Input.RawMouseActions, Int32, Int32, Int32)
   w System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr, MS.Internal.Interop.WindowMessage, IntPtr, IntPtr, Boolean ByRef)
   w System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
   w MS.Win32.HwndWrapper.WndProc(IntPtr, Int32, IntPtr, IntPtr, Boolean ByRef)
   w MS.Win32.HwndSubclass.DispatcherCallbackOperation(System.Object)
   w System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate, System.Object, Int32)
   w MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(System.Object, System.Delegate, System.Object, Int32, System.Delegate)
   w System.Windows.Threading.Dispatcher.InvokeImpl(System.Windows.Threading.DispatcherPriority, System.TimeSpan, System.Delegate, System.Object, Int32)
   w MS.Win32.HwndSubclass.SubclassWndProc(IntPtr, Int32, IntPtr, IntPtr)
   w MS.Win32.UnsafeNativeMethods.DispatchMessage(System.Windows.Interop.MSG ByRef)
   w System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame)
   w System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame)
   w System.Windows.Application.RunDispatcher(System.Object)
   w System.Windows.Application.RunInternal(System.Windows.Window)
   w System.Windows.Application.Run(System.Windows.Window)
   w Plan_G3._Main.Main()


and next:

Nazwa aplikacji powodującej błąd: Plan-G3.exe, wersja: 3.0.7.71, sygnatura czasowa: 0x525a9d7a
Nazwa modułu powodującego błąd: KERNELBASE.dll, wersja: 6.1.7601.18229, sygnatura czasowa: 0x51fb10c6
Kod wyjątku: 0xe0434352
Przesunięcie błędu: 0x0000812f
Identyfikator procesu powodującego błąd: 0xbd4
Godzina uruchomienia aplikacji powodującej błąd: 0x01cee603f40bf9d5
Ścieżka aplikacji powodującej błąd: C:\Program Files\TA Software\Plan-G v3\Plan-G3.exe
Ścieżka modułu powodującego błąd: C:\Windows\system32\KERNELBASE.dll
Identyfikator raportu: c843503a-51f7-11e3-b998-406186b36c56