Items wrongly appears as “Out of Stock”

Question

Suddenly I'm seeing that all the items in the inventory appears as "Out of Stock" but all of them has one or more items available (never zero). All the items are configurable products and the simple ones are no visible individually in the frontend.

The settings for the configurable products inventory are as follow:

Manage Stock: Yes (Use Config Settings)
Enable Qty Increments: Yes (Use Config Settings)
Qty Increments: 1 (Use Config Settings)
Stock Availabity: In Stock

The Settings for the simple products inventory are as follow:

Manage Stock: Yes (Use Config Settings)
Qty: 1
Qty for Item's Status to Become Out of Stock: 0 (Use Config Settings)
Minimum Qty Allowed in Shopping Cart: 0 (Use Config Settings)
Maximum Qty Allowed in Shopping Cart: 10000 (Use Config Settings)
Qty Uses Decimals: No
Backorders: No Backorders (Use Config Settings)
Notify for Quantity Below: 1 (Use Config Settings)
Enable Qty Increments: Yes (Use Config Settings)
Qty Increments: 1 (Use Config Settings)
Stock Availability: In Stock

Answer 1

The Problem was in the configurable product, which wasn't associated with any single product. The thing is: it was impossible to associate it with a single product (there were only three single ones) because none of those was listed in the Associated Products list.

So, I've just deleted and created it again and then the product display the correct stock in the frontend.