Heres a simplified version of what I've got: A rectangle with a drop shadow
with a transparancy maks masking out half of it.
I ended up with a shadow object (a blurred dark rectangle) and the white
rectangle on top. I group them and apply layer mask, then when I come to
flatten tranparancy the the white top rectangel and transparncy mask
dissappear leaving me with just the dark rectangle. Argh! It shouldn't be
this difficult!

Getho