SilveLight 4, System Reflection.TargetInvocationException: (Async_ExceptionOccurred)

Question

I am going to try to explain this the best I can. There is a web site I need to use because of the maps, well the website have silver light which run properly. On the website there is export file option, when I pressed export button "SaveFileDialog" box appeared on the screen. Here I choose the target file path/name to copy the already exported file to my target location on my desktop. This ZIP file generates by some other service located on path like "http:Servername:81/path/File/output.zip". When I export file on the same network (Inner network) it works properly but when I accessed the same site from some other network (Outer network) I got following exception

System Reflection.TargetInvocationException: (Async_ExceptionOccurred) Arguments: Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.60831.0&File=System.dll&Key=Async_ExceptionOccurred Check InnerException for exception details. ---> System.Security.SecurityException ---> System.Security.SecurityException: Security error. at System.Net.Browser.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult) at System.Net.Browser.BrowserHttpWebRequest.<>c__DisplayClass5.b__4(Object sendState) at System.Net.Browser.AsyncHelper.<>c__DisplayClass2.b__0(Object sendState) --- End of inner exception stack trace --- at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state) at System.Net.Browser.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult) at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result) at System.Net.WebClient.OpenReadAsyncCallback(IAsyncResult result) --- End of inner exception stack trace --- at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary() at System.Net.OpenReadCompletedEventArgs.get_Result() at NYSBridge.Utility.ArcGISLyrAndTblInfo.WebClient_OpenReadCompleted(Object sender, OpenReadCompletedEventArgs e) at System.Net.WebClient.OnOpenReadCompleted(OpenReadCompletedEventArgs e) at System.Net.WebClient.OpenReadOperationCompleted(Object arg)

Also I have placed clientaccesspolicy.xml and crossdomain.xml files on the root of the service running on the server "http:Servername:81/path/File/output.zip" but still I am getting the exception.

Following are the entries of my clientaccesspolicy.xml & crossdomain.xml files

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>

crossdomain.xml

<?xml version="1.0" ?>
<cross-domain-policy>
    <allow-access-from domain="*" />
    <site-control permitted-cross-domain-policies="all"/>
    <allow-http-request-headers-from domain="*" headers="*"/>
</cross-domain-policy>

Production environment is stuck due to this exception & I am expecting the quick response from you.

Thanks,

Zaheer