UI freezing despite of task

Try
    Dim tasks As New List(Of Task)()

    For Each drv In drives
        Dim currentDrive As Drive = drv
        If drv.IsReady Then
            Dim readTask As New Task(Sub()
                                         queryDrive(currentDrive)
                                     End Sub, TaskCreationOptions.LongRunning)
            tasks.Add(readTask)
            readTask.Start()
        End If
    Next

    'Task.WaitAll(tasks.ToArray())

    timerTotalMsStopwatch.Stop()
    btnGetComputers.Enabled = True
    btnCancel.Enabled = False

    Dim msg As String = String.Format("{0} files ({1:0} Sec).", files.Count, timerTotalMsStopwatch.ElapsedMilliseconds / 1000)
    SetUIText(msg, msg & vbCrLf)

Catch ex As Exception
    MsgBox(String.Format("{0}", ex.StackTrace), MsgBoxStyle.Critical, "Error")

End Try