Problem casting to an interface in flex

I am using interfaces for module communication like in adobe flex documentation. When I have a ModuleLoader in mxml, everything works great.

<mx:TabNavigator id="testNav"
                height="100%"
                width="100%">
        <s:ModuleLoader id="firstTab" 
                        label="ONE" 
                        width="100%"
                        url="path/to/module/Mod1.swf"/>

        <s:ModuleLoader id="secondTab"
                        label="TWO" 
                        width="100%"
                        url="path/to/module/Mod2.swf"/>


</mx:TabNavigator>

and i have this code

var someChild:* = firstTab.child as ISomeModule;

ISomeModule is the interface. But when I have a ModuleLoader in actionscript in another file, when I do the same thing, someChild becomes null when cast to ISomeModule

var myLoader:ModuleLoader=new ModuleLoader();
myLoader.percentHeight=50;
myLoader.percentWidth=50;
myLoader.loadModule(moduleURL + "?attr=value&attr2=" + parentDocument.attr2);

and in another function, I have

var childMod:* = myLoader.child as ISomeModule;

myLoader.child is not null but when cast to ISomeModule, it becomes null. Does anyone have an idea about how to solve this? thanks

2 things:

• You need the same ApplicationDomain for cross-module class sharing (you should also enable optimizing in your Module compilation): <s:ModuleLoader url="someURL" applicationDomain="{ApplicationDomain.currentDomain}" />
• If I remember correctly, it should be firstChild.content and not firstChild.child for the actual module itself.