VS 2010 RunWorkerCompleted Not Firing Consistently

''' <summary>
    ''' Refreshes the student list based on the value of the student refresh flag.
    ''' </summary>
    Private Sub RefreshStudents()
 
        Try
 
            'if not already busy
            If Not brwStudents.IsBusy Then
 
                oStudentLookup.Clear()
 
                'clear any existing rows
                grdStudents.PrimaryGrid.Rows.Clear()
 
                'update the status
                sStatusStudentMGT = "Retrieving student records..." : UpdateStudentManagementFooter()
 
                'set the now rows text
                grdStudents.PrimaryGrid.NoRowsText = "Retrieving student records..."
 
                'set the wait cursor
                grdStudents.UseWaitCursor = True
 
                'show progress
                pgbMain.Visible = True
 
                'retrieve the list students
                brwStudents.RunWorkerAsync(Me)
 
            Else 'already busy
 
                'cancel the current operation
                brwStudents.CancelAsync()
 
            End If 'if not already busy
 
        Catch ex As Exception
 
            'handle the exception
            MsgBox(ex.Message)
 
        End Try
 
    End Sub
 
Private Sub brwStudents_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles brwStudents.DoWork
 
        Try
 
            Dim fMain As frmLoad = TryCast(e.Argument, frmLoad)
 
            'if we have a main form (UI thread) reference
            If (fMain IsNot Nothing) Then
 
                Dim oGrid As SuperGridControl = fMain.grdStudents
                Dim bResult As Boolean = True
                Dim oWorker As System.ComponentModel.BackgroundWorker = CType(sender, System.ComponentModel.BackgroundWorker)
 
                'loop thru all the students
                For iIndex As Integer = 1 To 10000 Step 1
 
                    'exit the loop if cancellation is pending
                    If oWorker.CancellationPending Then e.Cancel = True : Exit For
 
                    'insert the student row
                    If Not UpdateDataRowStudent(oGrid, "ID:" & CStr(iIndex), "ID:" & CStr(iIndex), "First:" & CStr(iIndex), "Last:" & CStr(iIndex), True, True) Then bResult = False : Exit For
 
                Next iIndex
 
                'set the result
                e.Result = bResult
 
            End If 'if we have a main form (UI thread) reference
 
        Catch ex As Exception
 
            'set the result to false on error (exception will be stored in the Error property)
            e.Result = False
 
        End Try
 
    End Sub
 
 Private Sub brwStudents_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles brwStudents.RunWorkerCompleted
 
        Dim sErrorMessage As String = String.Empty
 
        Try
 
            'if no errors occurred during the request
            If (e.Error Is Nothing) Then
 
                'if we have a result
                If (e.Result IsNot Nothing) Then
 
                    'if the result was an exception
                    If (TypeOf e.Result Is Exception) Then
 
                        'set the error message
                        sErrorMessage = DirectCast(e.Result, Exception).Message
 
                    ElseIf Not CBool(e.Result) Then 'request failed for another reason
 
                        'set the error message
                        sErrorMessage = "List students failed."
 
                    ElseIf CBool(e.Result) Then 'request was successful
 
                        Dim oGridPanel As GridPanel = grdStudents.PrimaryGrid
 
                        'if we have rows
                        If (oGridPanel.Rows.Count > 0) Then
 
                            Dim oRow As GridRow = If(oGridPanel.ActiveRow Is Nothing, CType(oGridPanel.Rows(0), GridRow), CType(oGridPanel.ActiveRow, GridRow))
 
                            'select the 1st row
                            oGridPanel.ClearSelectedRows() : oGridPanel.SetSelected(oRow, True) : oGridPanel.SetActiveRow(oRow)
 
                        End If 'if we have rows
 
                    End If 'if the result was an exception
 
                Else 'unexpected result
 
                    'set the error message
                    sErrorMessage = "List students failed."
 
                End If 'if we have a result
 
            Else 'exception occurred
 
                'set the error message
                sErrorMessage = e.Error.Message
 
            End If 'if no errors occurred during the request
 
        Catch ex As Exception
 
            'set the error message
            sErrorMessage = ex.Message
 
        Finally
 
            'update the status
            sStatusStudentMGT = String.Empty : UpdateStudentManagementFooter()
 
            'if no errors occurred during the request
            If String.IsNullOrEmpty(sErrorMessage) Then
 
                'reset the now rows text
                grdStudents.PrimaryGrid.NoRowsText = "No students"
 
            Else 'errors occurred during the request
 
                'set the now rows text to the error message
                grdStudents.PrimaryGrid.NoRowsText = sErrorMessage
 
            End If 'if no errors occurred during the request
 
            'reset the wait cursor
            grdStudents.UseWaitCursor = False
 
            'hide progress
            pgbMain.Visible = False
 
        End Try
 
    End Sub
 
  Private Function UpdateDataRowStudent(ByRef oGrid As SuperGridControl, ByVal sGUID As String, ByVal sID As String, ByVal sFirstName As String, ByVal sLastName As String, ByVal bIsActive As Boolean, ByVal bIsNewRow As Boolean) As Boolean
 
        Try
 
            Dim bResult As Boolean
 
            'if we have a target grid
            If (oGrid IsNot Nothing) Then
 
                Dim oRow As GridRow
                Dim oPrimaryPanel As GridPanel = oGrid.PrimaryGrid
 
                'if a new row is to be inserted into the grid
                If bIsNewRow Then
 
                    Dim sRowData(GetType(StudentDataColumns).GetEnumNames.Count - 1) As Object
 
                    'instantiate an empty student row
                    oRow = New GridRow(sRowData)
 
                    'insert a new row (activate the row if an invoke is not required - new student)
                    InsertRowData(oPrimaryPanel, oRow)
 
                Else 'modify/update row
 
                    'reference the active student row
                    oRow = CType(oPrimaryPanel.ActiveRow, GridRow)
 
                End If 'if a new row is to be inserted into the grid
 
                'set the reference to the student's GUID in the row tag
                oRow.Tag = sGUID
 
                'store the student GUID
                UpdateCellData(oRow.Item(StudentDataColumns.GUID), sGUID)
 
                'store the student ID
                UpdateCellData(oRow.Item(StudentDataColumns.PublicID), sID)
 
                'store the student first name
                UpdateCellData(oRow.Item(StudentDataColumns.FirstName), sFirstName)
 
                'store the student last name
                UpdateCellData(oRow.Item(StudentDataColumns.LastName), sLastName)
 
                'store the active flag
                UpdateCellData(oRow.Item(StudentDataColumns.Active), bIsActive)
 
                'set the result
                bResult = True
 
                'if a new row is to be inserted into the grid
                If bIsNewRow Then
 
                    'add the student to the lookup table
                    If Not oStudentLookup.ContainsKey(sGUID) Then oStudentLookup.Add(sGUID, (sFirstName & " " & sLastName).Trim)
 
                Else 'modify/update row
 
                    'update the student to the lookup table
                    If oStudentLookup.ContainsKey(sGUID) Then oStudentLookup(sGUID) = (sFirstName & " " & sLastName).Trim
 
                End If 'if a new row is to be inserted into the grid
 
                'if in worker thread 
                If Not oGrid.InvokeRequired Then
 
                    'perform any layout logic (required in order to update the selection)
                    oGrid.ArrangeGrid()
 
                    'select the updated row
                    oPrimaryPanel.ClearSelectedRows() : oPrimaryPanel.SetSelected(oRow, True) : oPrimaryPanel.SetActiveRow(oRow)
 
                End If 'if in worker thread
 
            End If 'if we have a target grid
 
            'return the result
            Return bResult
 
        Catch ex As Exception
 
            'throw the exception
            Throw
 
        End Try
 
    End Function
 
 ''' <summary>
    ''' Thread-safe delegate used to handle the updating of a grid cell's data.
    ''' </summary>
    ''' <param name="oCell">A reference to the target cell.</param>
    ''' <param name="oData">The cell data.</param>
    Private Sub UpdateCellData(ByVal oCell As GridCell, ByVal oData As Object)
 
        Try
 
            'if we have a cell
            If (oCell IsNot Nothing) Then
 
                'if must invoke the method
                If (oCell.SuperGrid IsNot Nothing) AndAlso oCell.SuperGrid.InvokeRequired Then
 
                    'invoke the method on the UI thread
                    oCell.SuperGrid.BeginInvoke(New UpdateCellDataDelegate(AddressOf UpdateCellData), oCell, oData)
 
                Else 'invoke not required
 
                    'set the value
                    oCell.Value = If((oData Is Nothing), String.Empty, oData)
 
                End If 'if must invoke the method
 
            End If 'if we have a cell
 
        Catch ex As Exception
 
            'handle the exception
            MsgBox(ex.Message)
 
        End Try
 
    End Sub
 
 
    ''' <summary>
    ''' Delegate used to handle the updating of a grid cell's data.
    ''' </summary>
    ''' <param name="oCell">A reference to the target cell.</param>
    ''' <param name="eColor">The text color of the cell.</param>
    Private Sub UpdateCellColor(ByVal oCell As GridCell, ByVal eColor As Drawing.Color)
 
        Try
 
            'if we have a cell, set the color
            If (oCell IsNot Nothing) Then oCell.CellStyles.ReadOnly.TextColor = eColor : oCell.CellStyles.Default.TextColor = eColor
 
        Catch ex As Exception
 
            'handle the exception
            Throw
 
        End Try
 
    End Sub
 
    ''' <summary>
    ''' Thread-safe delegate used to handle the insertion of rows into a grid panel.
    ''' </summary>
    ''' <param name="oGridPanel">A reference to the target grid panel.</param>
    ''' <param name="oData">A reference to the data row.</param>
    Private Sub InsertRowData(ByVal oGridPanel As GridPanel, ByVal oData As GridRow)
 
        Try
 
            'if we have a grid panel and data
            If (oGridPanel IsNot Nothing) AndAlso (oData IsNot Nothing) Then
 
                'if an invoke is required
                If oGridPanel.SuperGrid.InvokeRequired Then
 
                    'invoke the method on the UI thread
                    oGridPanel.SuperGrid.BeginInvoke(New InsertRowDataDelegate(AddressOf InsertRowData), oGridPanel, oData)
 
                Else 'on UI thread
 
                    'add the data to the collection
                    oGridPanel.Rows.Add(oData)
 
                End If 'if an invoke is required
 
            End If 'if we have a grid panel and data
 
        Catch ex As Exception
 
            'handle the exception
            Throw
 
        End Try
 
    End Sub