CS6 Gradient to transparent not working??

Hi there,

I'm in a bit of a rush - so thanks for taking the time...

I have a gradient in CS6 which I have set from 0% white to 100% Spot Colour then back to 0% white as I want the gradient to be transparent at the edges.

For some reason the 0% is not displaying as transparent on the screen, even though in the Gradient editor it does show the trasparency is there.

Any ideas????