Access 2010 fails where 2007 worked

[Andolino]

In Access 2010 I get a Write Conflict error - "This record
has been changed by another user..."
In Access 2007 this Code is working - why?

Private Sub Form_BeforeUpdate(Cancel As Integer)
Dim dbs As DAO.Database, rst As DAO.Recordset, strCriteria As Variant

Set dbs = CurrentDb
       Set rst = dbs.OpenRecordset("Artikel", dbOpenDynaset)
       strCriteria = "[Artikel-Nr] =" & Me.[Artikel-Nr]
       rst.FindFirst (strCriteria)

If Not Me.NewRecord Then
        rst.Edit
        rst("Lagerbestand") = rst("Lagerbestand") + anzdif
        rst.Update
rst.Close
        Set rst = Nothing
        Set dbs = Nothing