I have no idea if I have done something or there is an issue somewhere but the product quantity field that normally sits next to the Add to Cart button has disappeared.
Check your settings for the quantity field. Here are all the options that have anything to do with it:
-> System -> Configuration -> tab Main -> Product -> option "Display the quantity field on the product page"
-> System -> Configuration -> tab Display -> Default parameters for products -> option "Quantity layout on product page"
Both options as above on each product edition page
Only for product listings, there is also the option "Quantity field on 'Add to cart' button" in the configuration of all your product listing menus/modules.
