Hi,

The shared data source refers to the connection information for the report data source so when it runs it uses the connection information stored on the server.

For the file share subscription you have to specify the username and password used to connect to the file share location. This connection information is allowing the report server to save the reports to the file location, this is not the same as the data source connection information.

You could as "doug.brown" says use a special reporting user for this connection. My view would be to create a view for the dds file share and save the connection information in the view.

HTH