OK, this is NOT a References problem (which is the common answer to posts on this error across many forums.)
I can update the table in question both manually and by query when I work on the back-end db. I get the error when trying to update it as a linked table in the front-end db, both manually and by query.
This is on my own machine so no question of different dlls etc.
I have also used the tables in question when linked into other front-end developments and never had this error.
There are no field or table validation rules anyway, nor is relational integrity enforced. The nearest we come to that is default values using Date() or Now() for date and time stamping records on insert. Again, the table in question has been in use for some time in other applications with no errors. All that I am trying to do is to update one field.