Silverlight: if your application doesn't run on the local server...

If you are having problems loading a Silverlight 2.0 application, and you have exhausted all options, you may need to register the XAP file extension in IIS. It is a simple fix. 

Open your IIS Manager, double-click on the MIME Types icon, and then on the Add... link on the right. 

Register the MIME type for .xap to application/x-silverlight-app.