While this problem deals with data sources in Excel, the data source in question is an Oracle database, and as the Oracle DBA it has fallen in my lap. I have lots of experience with Oracle, and lots of experience configuring desktops to use Oracle client, but none with Excel external data sources.
Given two desktops. Both running Windows 7 Pro 64 bit. One with Office 2007, one with Office 2012. Both with Oracle Client 11.2.
On the machine with Office 2007, no problem refreshing data from the data source.
On the machine with Office 2012, all attempts return “Initialization of the data source failed. Check the database server or contact your database administrator. Make sure the external database is available, and then try the operation again. …”
The database is most definitely available. I can connect to it from the failing machine using native oracle ‘sqlplus.exe’. The OLE provider “Microsoft Data Access – OLE DB Provider for Oracle” is installed and selectable as a data source when using the data connection wizard to create a new data source.
Thinking there might be a version incompatibility, I removed the Oracle 11.2 client and installed the newest 12.1 client, but had the same result as before.