subForms text box not editable

[JerryKlmns]

I have an unbound main form (frmProjects) with a combo (cmbProject) to select a record showning in 5 subforms its details

In subform frmMainData the recordsource is a query returning detail data for record selected in cmbProject

SELECT NoEnumerators.* 
FROM NoEnumerators 
WHERE ProjectID=[Forms]![frmProjects].[lblProjectID].[caption];

Text boxes on the subform are bound except for one (txt). On the doubleclick event of txtBenefit

Private Sub txtBenefit_DblClick(Cancel As Integer)
With txtBenefit
    myText = Left(CleanData(.Value, "Text"), 255)
    txt.Height = .Height
    txt.Top = .Top
    txt.Left = .Left
    txt.Width = .Width
    txt.Value = myText 
    txt.Visible = True
    txt.SetFocus
    .Visible = False
End With
End Sub

I move the unbound textbox over the double-clicked and set its value. Up to this point everything is fine. That unbound text box is not editable.

Does anyone have any clue why?