I created Hebrew website (rtl direction) http://dev.macam.ac.il/yoav/DNN/gilrach
i put "direction:rtl;" in the MainMenu_MenuContainer

.MainMenu_MenuContainer {
    border-bottom: #FFFFFF 0px solid;
    border-left: #E7EDE3 0px solid;
    border-top: #FFFFFF 0px solid;
    border-right: #404040 0px solid;
    background-color: #5e7c24;
    width: 1pt;
    padding: 0px;
    width:235px;
    height:500px;
    direction:rtl;
}

You'll notice that although the first  submenu  is fine, the second submenu  "forgets" the  rtl effect

(i added "First" =>  "Sub" => "Sub Sub" button to demonstrate it).

Help needed

yoav

rtl is not my expertise but from looking at the menu this is the way I would troubleshoot it.

For anyone else reading, this site gives info on the direction property

On your site use the web developers toolbar to identify additional classes that the menu maybe using which are overriding your own stylings coming from the MenuContainer class. - From there you will be able to add those classes and the direction property into your CSS.

I outline these techniques in this tutorial: Troubleshooting DotNetNuke Skins

Hope this helps,