Does the SKU field really come from the PubImport table occurrence the layout is based on? –
And does the SKU13 field really come from the BooksForImportISBN table occurrence that is related to the layout TO by SKU = SKU13?
If that's not the issue, then screenshots of your layout and relationship graph would be helpful.
Thanks for replying, erolst.
In order to make a smaller, and more easily screen-grabbed layout, I started a new one based on PubImport and added the SKU field from PubImport and SKU13 from BooksForImportISBN. These, of course, worked fine.
When I pasted those fields from the new layout to the problem one, they still work but, despite the data field being exactly the same in the Inspector, they show different data to the problem field on the original layout.
Expanding this, I just made another new layout using the wizard, and it works... I can only assume that I'd managed to get two layouts or tables or something with the same name, but I don't recall how.
BUT, thanks again for taking the time to reply.