After downloading a web application (XBAP, Silverlight, etc.) if you receive the message Trust Not Granted, then either there was a problem during the download or most likely you do not have a valid certificate installed.

If your certificate is installed, then retry the request (or refresh/F5).  If the error still occurs then your certificate may have expired.

Whether the certificate has expired or you need an initial certificate, it will need to be installed.  Please follow the instructions provided under Customer Support for your application or review the article on Certificates.