What I beleive I'm seeing is the first click selects the row, the second click selects the checkbox and the third click updates the value.
<telerik:RadGridView ScrollViewer.VerticalScrollBarVisibility="Auto" RowDetailsVisibilityMode="VisibleWhenSelected" RowIndicatorVisibility="Collapsed" IsSynchronizedWithCurrentItem="True" AutoGenerateColumns="False" ItemsSource="{Binding Path=WorkAccessSource.View, Mode=TwoWay}" SelectionUnit="FullRow" SelectedItem="{Binding CurrentWorkAccessObject, Mode=TwoWay, UpdateSourceTrigger=Default}" SelectionMode="Single">
....
<telerik:RadGridView.Columns>
....
<telerik:GridViewCheckBoxColumn Header="Caps" DataMemberBinding="{Binding CallForCaps, Mode=TwoWay, Converter={StaticResource CharToBooleanConverter}}" IsSortable="True" IsGroupable="True" IsFilterable="False" IsReadOnly="False" HeaderTextAlignment="Center" />
...
</telerik:RadGridView.Columns>