Away3d with interactive Flex Component as MovieMaterial

Question

I have managed to get a custom Flex component (based on a Tile) to render on to an Away3d plane as described at http://www.flashgamer.com/2008/08/using%5Faway3d%5Finside%5Fa%5Fflex%5Fapp.html

I cannot however set the object to be interactive. When setting

wallMaterial.interactive = true;

I end up with a "supplied index out of bounds" error.

I have the component sitting in my MXML file with visible=false. I then create my Away3d object and add the component as a MovieMaterial. I am assuming that the error is because the component is already in the display list and so cannot be referenced through the Away3d view.

Anyone done this before?