Run-time error 2763 DTPicker return the error: Property is read only

[billa1a]

I use the follow code in the load section of a form.
Private Sub Form_Load()
Me.StartDate.Value = Date
Me.EndDate.Value = Date
Select Case Month(Date)
Case 1 To 6
Me.SchoolYear.Value = DateSerial(Year(Date - 365), 7, 1)
Case Else
Me.SchoolYear.Value = DateSerial(Year(Date), 7, 1)
End Select
End Sub
The three DTPicker controls as set.
When I exit the application without closing the form, I get the error message above.
The application is Access 2003 with a SQL backend.