um...despite the fact that i've got rgba output selected when i look at my render pics in photoshop there is just a blank alpha.
Why is this?
did you place any enviroment in your scene that can cause the alpha to be blank? What file format do you use? What version of XSI and photoshop?
Your alpha exists but you have something which is blocking it like a bg col output shader. Check with the render region by turning on show alpha. Also make sure u have downloaded and installed the soft .pic reader for photoshop.