Thanks for your post Rob. However, there is a script manager on the page. This code is adding one of a number of controls on the page, tabs, treeview, splitter's etc, all of which are working fine.

Regards
Nick

Thanks Mike.

Hi Mike,

Works for a simple case, however my DataGrid is created as part of a more complex object.

My page code is....

Partial Class _Default
  Inherits System.Web.UI.Page

  Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
    BuildDataGrid()
  End Sub


  Private Sub BuildDataGrid()
    Dim ParentControl As New ParentControl
    Me.Form.Controls.Add(ParentControl)
  End Sub
End Class

The definition of ParentControl is ...

Imports Microsoft.VisualBasic
Imports Infragistics.Web.UI.GridControls
Imports System.Data

Public Class ParentControl
  Inherits WebControl

  Protected Overrides Sub CreateChildControls()
    BuildDataGrid()
  End Sub

  Private Sub BuildDataGrid()
    Dim DataGrid As New Infragistics.Web.UI.GridControls.WebDataGrid
    DataGrid.ID = "DataGrid"
    DataGrid.DataSource = GetDepartments()
    DataGrid.CssClass = "Default"

    DataGrid.Height = Unit.Percentage(100)
    DataGrid.Width = Unit.Percentage(100)

    DataGrid.AutoGenerateColumns = False
    DataGrid.EnableAjax = True

    Dim boundField1 As New BoundDataField(True)
    boundField1.Key = "DepartmentID"
    boundField1.Header.Text = "Name"
    'Bind to CompanyName field in data source
    boundField1.DataFieldName = "DepartmentID"

    Dim boundField2 As New BoundDataField(True)
    boundField2.Key = "DepartmentName"
    boundField2.Header.Text = "Name"
    'Bind to CompanyName field in data source
    boundField2.DataFieldName = "DepartmentName"
    ' At this point you can set up a template for the template column

    ' ADD COLUMNS
    DataGrid.Columns.Add(boundField1)
    DataGrid.Columns.Add(boundField2)

    If DataGrid.Behaviors.ColumnMoving Is Nothing Then
      DataGrid.Behaviors.Add(DataGrid.Behaviors.CreateBehavior(Of ColumnMoving))
    End If
    DataGrid.Behaviors.ColumnMoving.Enabled = True

    If DataGrid.Behaviors.ColumnResizing Is Nothing Then
      DataGrid.Behaviors.Add(DataGrid.Behaviors.CreateBehavior(Of ColumnResizing))
    End If
    DataGrid.Behaviors.ColumnResizing.Enabled = True

    If DataGrid.Behaviors.Filtering Is Nothing Then
      DataGrid.Behaviors.Add(DataGrid.Behaviors.CreateBehavior(Of Filtering))
    End If
    DataGrid.Behaviors.Filtering.Enabled = True

    If DataGrid.Behaviors.Sorting Is Nothing Then
      DataGrid.Behaviors.Add(DataGrid.Behaviors.CreateBehavior(Of Sorting))
    End If
    DataGrid.Behaviors.Sorting.Enabled = True


    DataGrid.DataBind()

    Me.Controls.Add(DataGrid)
  End Sub


  Private Function GetDepartments() As DataTable
    Dim dt As DataTable = New DataTable("Departments")
    dt.Columns.Add("DepartmentID", GetType(Integer))
    dt.Columns.Add("DepartmentName", GetType(String))

    For i As Integer = 0 To 8 Step 1
      dt.Rows.Add(New Object() {i, String.Format("Department {0}", i)})
    Next

    dt.PrimaryKey = New DataColumn() {dt.Columns("DepartmentID")}

    Return dt
  End Function
End Class

The problem still occurs in this case.

Thanks
Nick

Should have thought about the solution in more detail before posting. Changing ...

Protected Overrides Sub CreateChildControls()
    BuildDataGrid()
End Sub

to ...

Private Sub ParentControl_Init(sender As Object, e As System.EventArgs) Handles Me.Init
    BuildDataGrid()
End Sub

solved it. Thanks for the help Mike.

Nick