Silverlight security error connecting SharePoint

Scenario:
Wrote a small Silverlight application which was trying to display the title of the site using Client Object Model and to my surprise I got the following error :

{System.Security.SecurityException ---> System.Security.SecurityException: Security error.
at System.Net.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
at System.Net.BrowserHttpWebRequest.<>c__DisplayClass5.b__4(Object sendState)
at System.Net.AsyncHelper.<>c__DisplayClass2.b__0(Object sendState)
--- End of inner exception stack trace ---
at System.Net.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
at System.Net.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
at System.Net.WebClient.OpenReadAsyncCallback(IAsyncResult result)}

Solution:
This can be because of few reasons

1. Make sure the web URL used to create the Client context object exist and brows-able.

2. This might be because of missing client policy access file missing for the SharePoint Web Application not allowing you to connect. Create a new XML file named ClientAccessPolicy.xml with content below and save it to 'C:\inetpub\wwwroot\VirtualDirectories\80'

Note : Update policy file and port number as needed.

ClientAccessPolicy.xml:

<?xml version="1.0" encoding="utf-8" ?> 
  <access-policy>
    <cross-domain-access>
      <policy>
        <allow-from http-request-headers="*">
           <domain uri="*" /> 
        </allow-from>
        <grant-to>
          <resource path="/" include-subpaths="true" /> 
        </grant-to>
     </policy>
   </cross-domain-access>
  </access-policy>

Once you have the file copied to right location, do an IISReset and make sure you can access the file using following url :

http://servername:portno/clientaccesspolicy.xml
Note
This setting is only for Development Environment. Read the following article how to tweak the policy file for production environment.

Article:MSDN