No More Product Cover Images

[la000]

Hello,

I upgraded my store to 1.6.1.2, but I lost all the products thumbnails.

Products still have their images, but no more cover image.

(the product's image does not appear on some module on my store, like on the cart, or product list)

So I have to go on each product, and click on "cover" on one of the product's images.

But there is a lot of products. How can I do to apply the 1st picture of each product as cover image ?

Thanks a lot !