Generating a print preview will fail with the error 'Unable to connect to Server' if the map contains multiple services and includes a cached ArcGIS Server Local service.
KB35789<a href="http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=35789" target="_blank">http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=35789</a>Change the connection type used to access the cached map service(s). Use Manager or Visual Studio to remove the existing cached ArcGIS Server Local map service and add it back again using an ArcGIS Server Internet connection.