Bizarre "You must enter a value in the [....] field" error from Access OLEDB destination

Hi

I can't make sense of why this error is occurring.

I know what it means: it's exactly the error I get if I test by manually try to enter a new row in the destination Access table, without entering anything into the DayDate column (which is Required).  But why on earth am I getting this error from my SSIS package?

Here's what the Dataflow in the package does:

1. OLEDB Source is a query on an SQL Server database.  This gives a small resultset (c.20 rows), with columns DayDate (date) and Total (int).

2. A Derived Column component adds a column called CurrentDateTime (expressionGETDATE()).  This column is not the one causing the error.

3. OLEDB Destination connected to the Access database takes the three columns and maps them to the three columns in the Access table.

Now I run this from Visual Studio: no problems, everything works fine.  As soon as I deploy it to the server and try to run it from there, it fails with this error: as if I'd somehow deleted the mapping to the Access destination columnDayDate.

Here's how I've tried to debug this error:

a) Just in case the deployed version was somehow getting rows with a NULL in the input column mapped toDayDate (though there's no reason why it should), I added a Multicast and output the three columns also to a CSV file.  When deployed, the package still fails with the same error from the Access OLE DB destination: but the CSV file is perfect, with no missing values in the DayDate column.  So there's no problem with the input data.

b) Exported the package's project from its deployed location to an ISPAC file, and opened it in Visual Studio, in case it had become corrupt somehow.  The mapping to columnDayDate is there, absolutely fine, and the package works fine in Visual Studio.

c) Checked filesystem permissions to both the Access .accdb file and its containing folder.  The SQL Server Agent service account (which runs the package) has Full Control permission on both.

I'm completely confused.  Is this error message one of those evil ones that actually doesn't mean what it says, but is obscuring some other problem?