Unable to locate specified base class 'resources.style1.HelpButtonIcon' for component class

Question

Hi,
I have a Flex (4.1.0) project, which has many skinnable custom components. The application allows a user to choose another style which changes these skins via loading a new compiled CSS. These non-default skins are in a separate Flex project.  I've not had a problem with this method until now.
The custom component I am skinning contains several icons which are defined in the component like this:
[SkinPart(required="true", type="mx.core.IVisualElement")]
public var componentIconHelp:IFactory;
then I use the iconRendererFunction to return the appropriate component part:
private function iconRendererFunction(item:Object):IFactory
     //truncated method    
     return componentIconHelp;
Within the skin for "style1", I then have
<s:Skin xmlns:fx="http://ns.adobe.com/mxml/2009"
     xmlns:s="library://ns.adobe.com/flex/spark"
     xmlns:mx="library://ns.adobe.com/flex/mx"
     xmlns:style1="resources.style1.*">
<!-- host component -->
<fx:Metadata>
     [HostComponent("myApp.components.ButtonComponent")]
</fx:Metadata>
<fx:Declarations>
     <fx:Component id="componentIconHelp">
          <style1:HelpButtonIcon />
     </fx:Component>
</Declarations>
When I try to compile this, I get the "Unable to locate specified base class 'resources.style1.HelpButtonIcon' for component class 'resources.style1.ButtonComponentSkinInnerClass0'" error.
If I remove the HelpButtonIcon from the <fx:Component> declaration, and just put it in the main body of the skin, it compiles and renders, but I need it to be a component (there's multiple components I have to choose from to display, similar to the ButtonBar skin).
Any ideas why it's not compiling and what I need to do to achive this?
Thanks

Answer 1

Thanks, one step closer (or further away :-)
I tried adding the airspark.swc to the library path for the project and it made no difference so I added:
-external-library-path /Applications/Adobe Flash Builder 4/sdks/4.0.0/frameworks/libs/air/airspark.swc
to the external tools configuration and now get the error:
command line: Error: unable to open 'Flash'
The project itself runs fine, it's only the ASDocs that's causing problems.