I have the same thing though i tracked down the problem to default quantity field being set to 0. It needs to be 1 or something else. My problem is that I can't think of any easy way to change all those fields to 1 on all my products (I have 3500+ of them). I tested it by setting it manually on some of the products and it appeared just fine. So is there an easy way to change this field or do i have to find a way to set it when uploading my products?