I am using v.3.9h and for the last few days I have had customers purchase from the store but a few customers here and there are not receiving an invoice or showing their orders in their order history. They finish the transaction with paypal but the orders are not showing in their account that the purchase even happened. I don't show the order at all at the store. I have not updated anything or added anything new to the store that may have altered anything. This has just happened in the last couple of days. Why would it be happening randomly and not to everyone? It has been only a handful of customers. What can I do to fix it? I have had my store since Jan of 2010 and updated my zen cart to 1.3.9h in January 2011. This is the first time I have been having these issues.