This one might be obvious, I suppose, to people with experience with the Bulk Insert task from previous SQL Server versions, but this information it was new to me. I have now learned the cause of this error with the SSIS Bulk Insert task reading from a flat file connection manager:

Cannot bulk load because the file "C:\XYZ.txt" could not be opened. Operating system error code 3(The system cannot find the path specified.).

This little item from the Bulk Insert task documentation [1] tells the tale:

The source file that the Bulk Insert task loads can be on the same server as the SQL Server database into which data is inserted, or on a remote server. If the file is on a remote server, you must specify the file name using the Universal Naming Convention (UNC) name in the path.

This creates some design pains in the butt that I was not anticipating.

Dan