Getting the following error when doing a databind on a webdatagrid

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

System.InvalidOperationException was caught

  Message=DataKeyField is invalid

  Source=Infragistics4.Web.v11.2

  StackTrace:

       at Infragistics.Web.UI.Framework.Data.DataSourceAdapter.Select(DataSourceSelectArguments arguments)

       at Infragistics.Web.UI.Framework.Data.DataSourceObjectView.ExecuteSelect(DataSourceSelectArguments arguments)

       at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)

       at System.Web.UI.WebControls.DataBoundControl.PerformSelect()

       at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()

       at Infragistics.Web.UI.GridControls.WebDataGrid.DataBind()

       at FedSelectWeb.Risk_Terms.LoadListData() in C:\Projects\FedSelect\FedSelectWeb\FedSelectWeb\Settings\sfrtblRiskTerms.aspx.vb:line 131

  InnerException:

 Private Sub LoadListData()
        Try
 
      
        Dim sString As String = Nothing
        MySession.RiskTermsList = GetRiskTermsList(sString)
        gGrid.ClearDataSource()
        gGrid.DataSource = MySession.RiskTermsList
        gGrid.DataBind()
        Dim selectedRows As SelectedRowCollection = gGrid.Behaviors.Selection.SelectedRows
            selectedRows.Add(gGrid.Rows(0))
            RecordCount(1, RiskTermsList.Count)
        Catch ex As Exception
 
        End Try
    End Sub

The RiskTermsList is a collection that contains 2 fields, a string and a integer.
The string field has been assigned as the datakeyfield.

I have other grids with strings as keyfields..

any ideas?