I have set up a downloadable product according to the "How do i add downloads to products? make products downloadable?" document in Zen Cart.

Product displays out of stock when adding to the shopping cart

Setup:

Products Quantity Box Shows: No, Do not show Quantity Box
Warning: Does not show Quantity Box, Default to Qty 1

Product Qty Minimum: 1
Product Qty Maximum: 0
Product Qty Units: 1
Product Qty Min/Unit Mix: Yes
Products Quantity: 1000

Does anyone have any ideas?