I'm using MVVM along with this template:

   <Style TargetType="{x:Type igDP:DataRecordPresenter}">

                                <Setter Property="IsSelected"

                                        Value="{Binding DataItem.IsSelected, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" />

   </Style>

and I have a IsSelected property in my viewmodel:

    Private _IsSelected As Boolean

    Public Property IsSelected() As Boolean

        Get

            Return _IsSelected

        End Get

        Set(ByVal value As Boolean)

            If value = _IsSelected Then

                Return

            End If

            _IsSelected = value

            OnPropertyChanged("IsSelected")

        End Set

    End Property

Selection tracking seem to work fine until you scroll the grid and then random items become selected and selected items lose there selection.  I can see this by showing the IsSelected property field on the grid.  Is there something I'm doing wrong?