Ado Seek - Error 3251

When I try to use .addnew appers "Error 3251 This operation requested by the application is not supported by the provider".
Why? I must use this code to syncronize the recordset.
This method is OK for SqlServer?
There is a better method?

Dim rs As New ADODB.Recordset ' file xml
Dim rs2 As New ADODB.Recordset
Dim tmpfld As ADODB.Field
Dim sADO As String

sADO = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "\db2000.mdb" & ";Persist Security Info=False"
rs2.Index = "PrimaryKey"
rs2.CursorType = adOpenDynamic
rs2.Open "Tabella2", sADO, , , adCmdTableDirect
rs.Open App.Path & "\file.xml", "Provider=MSPersist"

rs.MoveFirst
While rs.EOF = False
     rs2.Seek Array(rs("CampoTesto")), adSeekFirstEQ
     If rs2.EOF Then
            rs2.AddNew  'THIS IS THE POINT!!!!!!!
     End If
     For Each tmpfld In rs.Fields
            'Debug.Print tmpfld.Name & " " & tmpfld.Value
            Select Case tmpfld.Name
               Case Else
                  If rs(tmpfld.Name).Type = 202 Then
                       If IsNull(rs(tmpfld.Name)) Then
                            rs2(tmpfld.Name) = ""
                         Else
                            rs2(tmpfld.Name) = rs(tmpfld.Name)
                       End If
                     Else
                       rs2(tmpfld.Name) = rs(tmpfld.Name)
                  End If
     End Select
     Next
     rs2.Update
     rs.MoveNext
  DoEvents
Wend

rs.Close
rs2.Close
Set rs = Nothing
Set rs2 = Nothing