Concurrency violation -> don't know why :s

Hello

here is my code :

VB Code:

Console.WriteLine(DsDozen1.Dozen.Rows(cmDozen.Position).Item("Opnameorientatie"))
' here opnameorientatie = 0                       
  DsDozen1.Dozen.Rows(cmDozen.Position).BeginEdit()
                        DsDozen1.Dozen.Rows(0).AcceptChanges()
                        Dim h As Integer = (CInt(DsDozen1.Dozen.Rows(cmDozen.Position).Item("Opnameorientatie")) + 90) Mod (CInt(System.Configuration.ConfigurationSettings.AppSettings("MaxDoosOpn")) + 90)
                        ' 'DsDozen1.Dozen.Rows(cmDozen.Position).Item("Opnameorientatie") = h
                     'here h = 90   DsDozen1.Dozen.Rows(cmDozen.Position).Item("Opnameorientatie") = h
                        'DsDozen1.Dozen.Rows(cmDozen.Position).EndEdit()
                        DsDozen1.Dozen.Rows(cmDozen.Position).EndEdit()
                        Try
                            cmDozen.EndCurrentEdit()
                            daDozen.Update(DsDozen1.Dozen)
'here i get a concurrencyerror
                            DsDozen1.Dozen.AcceptChanges()
                        Catch ex As Exception
                            Console.WriteLine(ex.Message)
                        End Try

Does anyone has an idea why i get a concurrency violation:
It says that there are no rows affected, but it really does affect a row...

plz help me

thx

Flyduck