Ther have been a number of threads on this issue, among them
but none of the suggestions or solutions in these threads or Microsoft technical articles apply. I think it must be an Access 2010 bug,
This was an Access 2003 database that I saved as a .accdb. I have been trying to edit a table in Datasheet view. There is no VBA code involved. The table has a primary key.
This is an "assignment" table that creates a many-to-many relationship between two other tables, and consequently has two fields, each of which is limited via a Lookup Wizard query to Query representing a selection from the table involved. In Datasheet view you can then select appropriate values for each field from a dropdown list.
The problem definitely does not come from the Lookup Wizard queries or indeed anything about the table structure. If I simply use Copy and Paste to duplicate the table, structure and all, the copy is updateable in Datasheet view the way I want it to be. But of course a number of other queries and reports depend on the original table, and you can't just substitute a copy in.
I think what corrupted the table was an occasion where I accidentally tried to select a duplicate entry for the primary key. The table was updateable up to that point, but after dismissing the dialog telling me my change would create a duplicate value, I began getting the "recordset is not updateable" message in the status bar.