Image not added to product

This has all previously worked fine, but since my client started to get someone else to add new products there seem to have been some problems.

My client has product images separated into relevant directories. When we try and add a new product, we use the Image Uploader (in Firefox) and add the relevant image. On the product page, under the images tab, the thumbnail of the image can be seen, however in the product list, it is showing up as if no image has been uploaded - the same goes for the product page on the front end.

In the database, in the product table, the Image field is blank. However, under the product_image table, there IS and image associated with the product! What is going on? Why is the product image url not being added to the product table but IS added to the product_image table?