Runtime error 3326 (1 Viewer)

Not quite sure where to put this one, as I don't know if it is a query issue, coding, or just form design?

I have attached a cut down copy of my database and the problem lies with when I try to update a date field in the subform.

To replicate the error, open the mainform, choose "Daily" & "Overdue". The subform should then appear with an "update" button next to the data. If you then choose update and select "yes" what should happen next is the "AssetDateLastSchedMaint" (long name I know) field should then be updated with todays date, the query rerun and all should be fine and dandy.

But, as usual I have run into a problem. When I choose to update the date I receive the error: "Runtime error 3326, This recordset is not updateable".

I actually based this form, subform, query and code on another in the same database and they all work fine . Could someone have a look for me and point out to me how to fix it.

Thanks in advance.

Runtime error 3326 - Recordset is not updateable

Should I be trying to update the table directly and not via the form?

The query that drives the subform is not updateable. Open the query in design view and unclick the summation button on the toolbar. This is the large backwards E. Note that the "Group By" modifiers disappear? Save the query. Retry your process. Note that the subform now shows the data but also allows you to add a new record? To suppress this behaviour, set the subform's AllowAdditions property = false.

Thanks very much for the pointer, that was indeed the source of my problem.