hello,
I have cut my scene down to the basic elements, a plane with 'use background' shader, a light and a sphere. i can hit render current frame, and on the alpha channel i can see my shadow. however when i batch render, the alpha channel has gone.

Ive tried all sorts to isolate my problem. i had it all working fine before but not sure where i went wrong.
i know this is a little vague but does is sound familiar to anyone. using tiffs/alpha checked under cam setting

if anyone can shed light on this, i would be very grateful
j