We are using a RadMaskedDateTimeInput in a very simple UserControl. 
Everything runs well at runtime, but at design time we get frequently the following exception. If you reload the VS2010-Designer usually the exception vanishes.

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System.Exception
The component 'Telerik.Windows.Core.Design.Resources.SharedResourcesDictionary' does not have a resource identified by the URI '/Telerik.Windows.Core.Design;component/resources/sharedresourcesdictionary.xaml'.
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at Telerik.Windows.Core.Design.Resources.SharedResourcesDictionary.InitializeComponent()
at Telerik.Windows.Core.Design.Resources.SharedResourcesDictionary.get_Instance()
at Telerik.Windows.Core.Design.SmartTagPaneBase.OnApplyTemplate()
at System.Windows.FrameworkElement.ApplyTemplate()
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at Microsoft.Windows.Design.Interaction.AdornerPanel.MeasureOverride(Size availableSize)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at MS.Internal.Interaction.BaseAdornerLayout.Measure(UIElement adorner, Size constraint)
at MS.Internal.Interaction.AdornerLayer.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.ContextLayoutManager.UpdateLayout()
at System.Windows.ContextLayoutManager.UpdateLayoutCallback(Object arg)
at System.Windows.Media.MediaContext.InvokeOnRenderCallback.DoWork()
at System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

Hello Peter,

We tried to reproduce this design time exception in VS 2010 with RadMaskedDateTimeInput from Q2 2014 dlls but we did not succeed. Is it possible for you to isolate this in a runnable sample and send it to use in a separate support thread ? Which version of RadControls do you use ? Thank you in advance for your cooperation.

Regards,
Petar Mladenov
Telerik