Currently, you can't set properties on individual datapoints with a binding in xamWebChart, so this line is your problem:

<igChart:Series.DataPoints>                              

   <igChart:DataPoint Label="Vacation Accrual" Value="{Binding Path=VacationAccrual, Converter={StaticResource DoubleConverter}}" />                                    

</igChart:Series.DataPoints>

Since DataPoint derives directly from DependencyObect, you can't set bindings on it from Xaml in the current version of Silverlight.

I've created a sample with a workaround, however, based on what I think you are describing. The gist is that its binding against a collection and using DataMapping even though its just one data point.

The Xaml:

<UserControl

    xmlns:dataFormToolkit="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm.Toolkit" 

    xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data" 

    x:Class="SilverlightApplication2.MainPage"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480"

    xmlns:igTileView="clr-namespace:Infragistics.Silverlight.Controls;assembly=Infragistics.Silverlight.XamWebTileView.v9.2"

    xmlns:igChart="clr-namespace:Infragistics.Silverlight.Chart;assembly=Infragistics.Silverlight.DataVisualization.Chart.v9.2"

    >

    <UserControl.Resources>

        <DataTemplate x:Key="UserTemplateMaximized">

            <StackPanel>

                <dataFormToolkit:DataForm x:Name="employeeDetailsForm" CurrentItem="{Binding}">

                    <dataFormToolkit:DataForm.ReadOnlyTemplate>

                        <DataTemplate>

                            <StackPanel>

                                <dataFormToolkit:DataField Label="Name">

                                    <TextBlock Text="{Binding Name}" />

                                </dataFormToolkit:DataField>

                                <dataFormToolkit:DataField Label="Vacation Accrual">

                                    <TextBlock Text="{Binding VacationAccrual}" />

                                </dataFormToolkit:DataField>

                            </StackPanel>

                        </DataTemplate>

                    </dataFormToolkit:DataForm.ReadOnlyTemplate>

                </dataFormToolkit:DataForm>

                <igChart:XamWebChart Name="webChart" Width="300" Height="200">

                    <igChart:XamWebChart.Legend>

                        <igChart:Legend Visibility="Collapsed" />

                    </igChart:XamWebChart.Legend>

                    <igChart:XamWebChart.Series>

                        <igChart:Series ChartType="Column" DataPointColor="Different" DataSource="{Binding AsCollection}"

                                        DataMapping="Value = VacationAccrual; Label = VacationAccrualLabel">

                        </igChart:Series>

                    </igChart:XamWebChart.Series>

                </igChart:XamWebChart>

            </StackPanel>

        </DataTemplate>

        <DataTemplate x:Key="UserTemplateNormal">

            <StackPanel>

                <dataFormToolkit:DataForm x:Name="employeeDetailsForm" CurrentItem="{Binding}">

                    <dataFormToolkit:DataForm.ReadOnlyTemplate>

                        <DataTemplate>

                            <StackPanel>

                                <dataFormToolkit:DataField Label="Name">

                                    <TextBlock Text="{Binding Name}" />

                                </dataFormToolkit:DataField>

                                <dataFormToolkit:DataField Label="Vacation Accrual">

                                    <TextBlock Text="{Binding VacationAccrual}" />

                                </dataFormToolkit:DataField>

                            </StackPanel>

                        </DataTemplate>

                    </dataFormToolkit:DataForm.ReadOnlyTemplate>

                </dataFormToolkit:DataForm>

            </StackPanel>

        </DataTemplate>

        <DataTemplate x:Key="UserTemplateMinimized">

            <StackPanel Orientation="Horizontal">

                <TextBlock Text="Name: "/><TextBlock Text="{Binding Name}"/>

            </StackPanel>

        </DataTemplate>

        <DataTemplate x:Key="HeaderTemplate">

            <TextBlock Text="{Binding Name}"/>

        </DataTemplate>

    </UserControl.Resources>

    <Grid x:Name="LayoutRoot">

        <igTileView:XamWebTileView Name="xamWebTileView1"

                                   MaximizedStateChanging="XamWebTileView_MaximizedStateChanging"

                                   ItemsSource="{Binding EmployeeCollection}"

                                   TilePaneContentTemplate="{StaticResource UserTemplateNormal}"

                                   TilePaneHeaderTemplate="{StaticResource HeaderTemplate}"

                                   >

        </igTileView:XamWebTileView>

    </Grid>

</UserControl>

With code behind:

public partial class MainPage : UserControl

    {

        public MainPage()

        {

            InitializeComponent();

            this.DataContext = this;

        }

        private void ChangeActiveTemplate(string templateName, UIElement element)

        {

            TilePane tile = element as TilePane;

            if (tile != null)

            {

                tile.ContentTemplate = this.Resources[templateName] as DataTemplate;

            }

        }

        private void SetAllOthersTemplate(string templateName, UIElement element)

        {

            foreach (UIElement child in xamWebTileView1.Items)

            {

                if (element != child)

                {

                    ChangeActiveTemplate(templateName, child);

                }

            }

        }

        private void XamWebTileView_MaximizedStateChanging(object sender, Infragistics.Silverlight.TileStateChangingEventArgs e)

        {

            TilePane tile = e.Element as TilePane;

            if (tile != null)

            {

                if (e.NewState == Infragistics.Silverlight.TileState.Maximized)

                {

                    SetAllOthersTemplate("UserTemplateMinimized", e.Element);

                    ChangeActiveTemplate("UserTemplateMaximized", e.Element);

                }

                else if (e.NewState == Infragistics.Silverlight.TileState.Normal)

                {

                    SetAllOthersTemplate("UserTemplateNormal", e.Element);

                    ChangeActiveTemplate("UserTemplateNormal", e.Element);

                }

                else

                {

                    ChangeActiveTemplate("UserTemplateMinimized", e.Element);

                }

            }

        }

        private EmployeeCollectionViewModel _employeeCollection;

        public EmployeeCollectionViewModel EmployeeCollection

        {

            get

            {

                if (_employeeCollection == null)

                {

                    _employeeCollection = new EmployeeCollectionViewModel();

  //test data

                    _employeeCollection.Add(new EmployeeViewModel() { Name = "Bob", VacationAccrual = 10 });

                    _employeeCollection.Add(new EmployeeViewModel() { Name = "Jessie", VacationAccrual = 10 });

                    _employeeCollection.Add(new EmployeeViewModel() { Name = "Jill", VacationAccrual = 4 });

                    _employeeCollection.Add(new EmployeeViewModel() { Name = "James", VacationAccrual = 13 });

                    _employeeCollection.Add(new EmployeeViewModel() { Name = "Brian", VacationAccrual = 20 });

                }

                return _employeeCollection;

            }

        }

    }

    public class EmployeeCollectionViewModel : ObservableCollection<EmployeeViewModel>, INotifyPropertyChanged

    {

        public EmployeeCollectionViewModel()

        {

        }

    }

    public class EmployeeViewModel

    {

        public string Name { get; set; }

        public double VacationAccrual { get; set; }

        public string VacationAccrualLabel { get { return "VacationAccrual"; } }

        public IEnumerable AsCollection

        {

            get

            {

                return new List<EmployeeViewModel>() { this };

            }

        }

    }

In particular, I'm not certain what you intended the UserTemplateMaximized for, from the information you provided, so I made an educated guess. Does this help?

-Graham

what are the exception details?

do you have a sample project you could send?  i'm not familiar with your setup using a DataField, so i'm uncertain how to reproduce the problem.