I am able to import metadata to my designer and construct my Dataflow.
Wehn I go to run my Job, however, I am receiving an error saying that 'The login is from an untrusted domain and cannot be used with Windows authentication'.
The Job Server is logging in with a System user account and as far as I know - that account was added to the Group which allows access to the SQL server.
Has anyone seen this issue before - and if so - please tell me how to explain to the windows folks so they can resolve this?
Double check that the Windows domain account indeed has access to the SQL Server. This is likely not a Data Services issue but a Windows Domain configuration issue. I have seen similar untrusted domain errors before and they resulted from changes to Windows domain controllers, where the trust between domains broke down. Sometimes this can occur if on of the domain controllers goes down and other domain controllers are no longer able to utilize it to do trust lookups.
The best thing to do is test the login of the account running your Job Server outside of any Data Services application. Can you log onto the Job Server as the user that runs the Job Service and then attempt to log into SQL via SQL Server Management Studio, perhaps? If you can log into SQL this way then the Job Server will be able to access SQL.