i have been key in every single serial number of each product when the shipment is arrived. all is good. but when i done create SO and do the DO to customer, i can choose the particular serial number but when i click on the validate, it show upw up "this serial number already in stock." i have no idea on how to solve this because i can see this particular serial number already in my stock, but cannot be validate on DO process and keep on showing "this serial number already in stock." error. anyone can help on this?