Problems with masking PNG file

[nikolatesla]

HI there,

I have a problem that need urgent fix. I have a image PNG which I would like to mask, however following the tutorial on masking I was not able to do it. I have managed to mask two vector shapes and that seems to work fine but I am not able to mask PNG image with the vector shape on top as a second layer.

What I want to have is a sun rising behind trees, if this helps.
My question is can this be done and how.

Pleasae help!

If you are interested I can email you sample of the Moho file...[/img]