When accessing www.google.com using Silverlight Web Browser control it throws an exception "Attempted to perform an unauthorized operation"

When i try to access a url from a web browser control in my silverlight app, i am getting an UnauthorizedAccessException saying "Attempted to perform an unauthorized operation".

ContactDetailsBrowser is the name of my web browser control.Following line is the one that throws the exception.

ContactDetailsBrowser.Source = new Uri("http://www.google.lk");

Please help.