THAT code. This page ate my XML...

      <root>

          <menuitem label="MenuItem A" icon="myTopIcon">

               <menuitem label="SubMenuItem A-1" enabled="False"/>

               <menuitem label="SubMenuItem A-2"/>

          </menuitem>

          <menuitem label="MenuItem B" type="check" toggled="true"/>

          <menuitem label="MenuItem C" type="check" toggled="false" icon="myTopIcon"/>

          <menuitem type="separator"/>

          <menuitem label="MenuItem D" icon="myTopIcon">

               <menuitem label="SubMenuItem D-1" type="radio" groupName="one">

                    <menuitem label="SubMenuItem D-2" type="radio" groupName="one">

                         <menuitem label="SubMenuItem D-3" type="radio" groupName="one" />

                    </menuitem>

               </menuitem>

               <menuitem label="SubMenuItem D-2" type="radio" groupName="one" toggled="true"/>

               <menuitem label="SubMenuItem D-3" type="radio" groupName="one"/>

          </menuitem>

     </root>

Dear jrunrandy

Thank you for your interest in this matter.

I isolated the issue by trimming away all unnecessary code. Have a look at the following MXML Application:

<?xml version="1.0" encoding="utf-8"?>

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"

                                 xmlns:s="library://ns.adobe.com/flex/spark"

                                 xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">

    <fx:Declarations>

        <fx:XML id="myData" xmlns="">

            <menu>

                <menuitem label="Level 0" icon="myTopIcon">                                

                    <menuitem label="Level 1" type="radio" groupName="one">                                  

                        <menuitem label="Level 2" type="radio" groupName="one">

                            <menuitem label="Level 3" type="radio" groupName="one" />                

                        </menuitem>

                    </menuitem>                               

                </menuitem>

            </menu>

         </fx:XML>

    </fx:Declarations>

     <mx:MenuBar

         dataProvider="{myData}"

         width="100%"

         labelField="@label"

         showRoot="false"/>

</s:Application>

IMHO, this code should render a menu resembling to this hierarchical structure:

Level 0

    -> Level 1

            -> Level 2

                     -> Level 3

However, the menu that is rendered resembles to this structure (also check the attached screen shot):

Level 0

   -> Level 1

           -> Level 3