Flex iOS Packaging: cannot find AppIcons

My AppIcons are defined in a custom application descriptor:

<icon>
    <image29x29>AppIcon29.png</image29x29>
    <image36x36>AppIcon36.png</image36x36>
    <image48x48>AppIcon48.png</image48x48>
    ... full list omitted for brevity
</icon>

And I have placed the icons in the src directory in the project structure as well as in an icon subdirectory:

I've located these files in multiple locations and updated the paths in the application descriptor definitions and no matter what I try, when packaging the app for debugging on a device it shows this error:

I'm obviously missing something here. Any ideas? Thanks!

Erik