Flash - problemas con importacion de clases

Estoy haciendo un proyecto flash donde utilizo el componmente window y el alert pero al poner las instruciones para importar las clases :

import mx.managers.PopUpManager;
import mx.containers.Window;
import mx.controls.Alert ;

me da los sgtes errores

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\core\UIObject.as: Line 46: The name of this class, 'mx.core.UIObject', conflicts with the name of another class that was loaded, 'mx.core.UIObject'.
class mx.core.UIObject extends MovieClip

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\managers\DepthManager.as: Line 16: The name of this class, 'mx.managers.DepthManager', conflicts with the name of another class that was loaded, 'mx.managers.DepthManager'.
{

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\events\EventDispatcher.as: Line 15: The name of this class, 'mx.events.EventDispatcher', conflicts with the name of another class that was loaded, 'mx.events.EventDispatcher'.
{

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\core\UIComponent.as: Line 40: The name of this class, 'mx.core.UIComponent', conflicts with the name of another class that was loaded, 'mx.core.UIComponent'.
class mx.core.UIComponent extends UIObject

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\managers\PopUpManager.as: Line 24: The name of this class, 'mx.managers.PopUpManager', conflicts with the name of another class that was loaded, 'mx.managers.PopUpManager'.
{

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\skins\RectBorder.as: Line 16: The name of this class, 'mx.skins.RectBorder', conflicts with the name of another class that was loaded, 'mx.skins.RectBorder'.
class mx.skins.RectBorder extends Border

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\core\ExternalContent.as: Line 12: The name of this class, 'mx.core.ExternalContent', conflicts with the name of another class that was loaded, 'mx.core.ExternalContent'.
{

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\core\View.as: Line 19: The name of this class, 'mx.core.View', conflicts with the name of another class that was loaded, 'mx.core.View'.
class mx.core.View extends UIComponent

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\controls\SimpleButton.as: Line 21: The name of this class, 'mx.controls.SimpleButton', conflicts with the name of another class that was loaded, 'mx.controls.SimpleButton'.
class mx.controls.SimpleButton extends UIComponent

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\skins\CustomBorder.as: Line 16: The name of this class, 'mx.skins.CustomBorder', conflicts with the name of another class that was loaded, 'mx.skins.CustomBorder'.
class mx.skins.CustomBorder extends Border

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\core\ScrollView.as: Line 57: The name of this class, 'mx.core.ScrollView', conflicts with the name of another class that was loaded, 'mx.core.ScrollView'.
class mx.core.ScrollView extends View

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\containers\Window.as: Line 35: The name of this class, 'mx.containers.Window', conflicts with the name of another class that was loaded, 'mx.containers.Window'.
class mx.containers.Window extends ScrollView

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\controls\TextArea.as: Line 27: The name of this class, 'mx.controls.TextArea', conflicts with the name of another class that was loaded, 'mx.controls.TextArea'.
class mx.controls.TextArea extends ScrollView

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\controls\Button.as: Line 29: The name of this class, 'mx.controls.Button', conflicts with the name of another class that was loaded, 'mx.controls.Button'.
class mx.controls.Button extends SimpleButton

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\controls\alertClasses\AlertForm.as: Line 23: The name of this class, 'mx.controls.alertClasses.AlertForm', conflicts with the name of another class that was loaded, 'mx.controls.alertClasses.AlertForm'.
class mx.controls.alertClasses.AlertForm extends UIComponent

**Error** C:\Documents and Settings\yormy\Local Settings\Application Data\Macromedia\Flash 8\en\Configuration\Classes\mx\controls\Alert.as: Line 25: The name of this class, 'mx.controls.Alert', conflicts with the name of another class that was loaded, 'mx.controls.Alert'.
class mx.controls.Alert extends Window

Total ActionScript Errors: 16 Reported Errors: 16

y cuandolas quito no me crea los componentes ya que los instancio dinamicamente,

por ayudenme