How are you trying to capture the Silverlight right-click action i.e. what steps are you trying to execute to capture it? Specifically, what Telerik product and version are you trying to use?
In the screenshot you provided it appears to be the standard popup you get with all Silverlight applications. We suspect this is normal behavior as right-clicks are not typically captured. What is the purpose to trying to capture this standard behavior of the Silverlight run time engine?
All the best,
the Telerik team