Error at check out

I have tried several times to purchase and keep getting the error and it will not process.  This is very frustrating with the holidays close.  I had this problem last week and it cancelled an order.  I was able to reorder at that time.  I moved to walmart because of the savings.  I had the same items to purchase at amazon, but it was $18 in shipping and walmart offered free shipping.  I am going to have to go back to ordering from amazon soon due to the dealine of christmas if this is not resolved soon.