I am having the same issue!!! it is very irritating.  All of my products are set up the same way.  Most things are decreasing the inventory module amount like they are supposed to be, but some items are not.  Every month I have to print my inventory module and calculate the cost of the items that are taken out at zero!  Most months, it is between $4000 - $6500.  Then I have to do a journal entry to adjust the inventory module and COGS.  This is very time consuming and NEEDS TO BE FIXED ASAP!  We pay taxes at the end of the year based on the amount in our inventory module, and if products are not decreasing this amount when they are sold, we are overpaying taxes.  I don't understand why it would be on some products and not others if all of the products are set up the same way.  This is definitely a Quick Books problem. I have attached a quick report on just one product.  You can see that it is very random.  Sometimes it has a cost, and sometimes it doesn't!