New Post: DataGrid + TimePicker + PropertyChanged

Me again,
a very big fault.
As soon i get two of this columns: with the '.' syntx, there is no more binding .

<xcdg:Column FieldName="StartWorkAt" x:Name="start">
<xcdg:Column.CellContentTemplate>

<DataTemplate>
                    <tkt:TimePicker Value="{Binding . , Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" TimeInterval="0:15"></tkt:TimePicker>
                </DataTemplate>
            </xcdg:Column.CellContentTemplate>
        </xcdg:Column>

<xcdg:Column FieldName="the SecondOne" x:Name="start">
<xcdg:Column.CellContentTemplate>

<DataTemplate>
                    <tkt:TimePicker Value="{Binding . , Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" TimeInterval="0:15"></tkt:TimePicker>
                </DataTemplate>
            </xcdg:Column.CellContentTemplate>
        </xcdg:Column>

Any ideas.
Thanks