VBA Query won't Edit

Can someone point out why this code crashes at the .Edit saying  that the database or query is read-only?

The code is set in an Access 2010 front-end linked to a SQL Server database.

The Access file is not read only - lots of similar procedures run OK.

The dataset the query produces is updateable - i can open it manually and change the DistributeOrderCard field.



Sub TestCust()
Dim db As Database
Dim recust As Recordset

Set db = CurrentDb()

'open customers
    Set recCust = db.OpenRecordset("qry101DistNewOrderCards", dbOpenDynaset, dbSeeChanges)
'test
    recCust.Edit
    recCust![DistributeOrderCard] = False
    recCust.Update
End Sub