I have a problem with the control for silverlight RadRichTextBox 4.

 my code is just <telerik:RadRichTextBox />

 and the error message is:

 Error HRESULT E_FAIL has been returned from a call to a COM component.
    to MS.Internal.XcpImports.CheckHResult (UInt32 hr)
    to MS.Internal.XcpImports.FrameworkElement_MeasureOverride (FrameworkElement element, Size availableSize)
    to System.Windows.FrameworkElement.MeasureOverride (Size availableSize)
    to System.Windows.FrameworkElement.MeasureOverride (IntPtr nativeTarget, inWidth Single, Single inHeight, outWidth Single &, Single & outHeight)

 telerik is my version: RadControls for Silverlight, v.2011.3.1220.1040 (Dev)

 could you help me?

Hello Thierry,

We are not able to determine the cause of the problem with a great certainty with the information you have provided. We have some ideas though. You can also check if all referenced Telerik assemblies have the same version. Also please make sure you have referenced all required assemblies:
http://www.telerik.com/help/silverlight/radrichtextbox-frequently-asked-questions.html#Assembly_References

Hope this helps.

Regards,
Mike
the Telerik team

I checked the telerik assemblies all have the same version. And I have all the requiredassemblies. 

Hello Thierry,

Given the information you provided we cannot tell what the problem is. We would very much appreciate a sample project illustrating the issue.

Pease get back to us so we can assist you further.

Regards,
Andrew
the Telerik team