My client has a Zen Cart store with 1.3.7 installed and is using the Products with Attributes Stock module.

If they set a quantity to "0" the customers can still buy the product with attribute. Help!

Here's my Admin > Configuration > Stock settings:

Check stock level - true
Subtract stock - true
Allow Checkout - false
Stock Re-order level- 2
Products status in Catalog when out of stock should be set to - 1
Show Sold Out Image in place of Add to Cart - 1
Product Quantity Decimals - 0
Show Shopping Cart - Delete Checkboxes or Delete Button - 3
Show Shopping Cart - Update Cart Button Location - 3
Show New Products on empty Shopping Cart Page - 1
Show Featured Products on empty Shopping Cart Page - 2
Show Special Products on empty Shopping Cart Page - 3
Show Upcoming Products on empty Shopping Cart Page - 4