When I was moving a site from one server to another, using TFS to deploy the reports to a Report Library in SharePoint 2010, I got the following error:
The shared data source ‘‘ for the report server or SharePoint site is not valid
The fix is not pretty, but it’s fairly easy to fix (at least in my case)

There were 2 things I had to make sure of. First, in the Report Library, I clicked on the ‘down arrow’ beside the link to the report and chose ‘Manage Data Sources’. when I got to the next page, I saw the correct Data Source name, and the fact that it was shared, but it turns out, it was not enough. It was disconnected somehow. I clicked on the link for the datasource name and saw that the path to the data source was missing. So, I had to browse to the correct data source and click OK. Like I said this was the first step, and for each report, I had to duplicate the same step each time.

The second thing is to go to the Report Data Sources folder, click the link for the Data Source, make sure of the connection string, but most of all, once the connection string and credentials are correct, in between the ‘Test Connection’ button (which you should click), and the ‘OK’ button, there’s a check box – ‘Enable this Data Source’. Make sure it’s checked, or you will get this error:
The report server cannot process the report. A data source associated with the report has been disabled