Lester,

Thanks for your reply.

>
> How is the calculated string created?
>

In the Datamodule/TQuery/OnCalculated event.
The calculated column does not use any Keys.

> Does the Edit work if you just use fields from the query in
> the grid?
>

No.

> Don't use calculated stuff myself, but I believe there is a
> flag to identify a calculated field so that the automatic
> stuff ignores it.
>

I've tried removing the calculated field and I still get
the 'cannot edit current row' error when the attempt is made
to put the datasource into Edit.