This error may be caused because of insufficient permissions to open the data source. Check the properties of the data source in the Reporting Services web interface. If it is set to use Windows Authentication, it is possible that the user does not have sufficient privileges to open the data source.

To resolve this problem, either grant the users permission to connect to the data source, or set a default username and password to connect to the data source.

This is the error that you may see:

An error has occurred during report processing. (rsProcessingAborted) Cannot create a connection to data source ‘xxx’. (rsErrorOpeningConnection)