Having installed my package onto the pre-production environment, and ironed out a heap of database permissions problems, I found myself contemplating the following error...

Error: 2006-08-22 13:56:32.93
  Code: 0xC002F210
  Source: Get Data
  Description: Executing the query "EXEC PRC_DATA_SEL ?" failed with the following error: "End tag 'Description' does not match the start tag 'ROOT'.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly.
End Error

When I connect to the pre-production database via my dev package having changed the configuration file, it functions as expected without a problem. So it isn't a database problem. When I change the pre-production configuration to point at my dev database, I get problems - so it looks like a machine related problem.

I then put Integration Services on to another test machine, and tried from there, and had success. So there was obviously something different about our pre-production box to both my dev environment and my newly borrowed test kit. The OS's were different, so I then spent a frantic 5 minutes checking that Integration Services should run on Windows 2000 Server SP4 - which it should.

Finally, I decided to install SP1 on my test (previously working) machine, and that too stopped working - not with exactly the same error but at this stage that was good enough. So, I've rolled back the pre-production environment to be pre-SP1 and now the package runs.

Not a great solution, but it'll do for the moment. Next step - upgrade my dev environment to be SP1 and re-work as necessary. And the moral of this story is always ensure your dev environment matches your pre-production and live. I'm glad I found out before the live stage though :-)