Alpha map shadow problem

Hi all,

I have made an intro animation of a card opening. The card has a die-cut pattern which I have used an alpha map to cut out the card. It works fine, except that the shadow that falls on the card is not based on the cut-out alpha, but the polygon plane of the card, which is a rectangle.

Ho do I get the cut-out pattern to cast the correct shadow instead of the bounding rectangle frame.

The main spotlight source shadow is cast using area shadow settings and I have checked to make sure the transparency in the render setting is turned on.

What could have caused this?

Ken