Repeated problem in 4.52 cart version on a 5.6.3 install. Customers place orders on now increasingly often the only notification is an email from Authorize.net. No order shows in the site and in the Event Viewer a bright blue tag with the following:

12/5/2011 2:23:26 PM Admin Alert Karin Schichtel Hackett Catholic Central Spirit Store
Stacktrace: : at Smith.DNN.Modules.BuyNow.Confirm.AddStoreOrder(I ...
Stacktrace: : at Smith.DNN.Modules.BuyNow.Confirm.AddStoreOrder(Int32 PayHistID, String orderStatus) at Smith.DNN.Modules.BuyNow.Confirm.ProcessStatus(PaymentStatusInfo status) at Smith.DNN.Modules.BuyNow.Confirm.Submit() at Smith.DNN.Modules.BuyNow.Confirm.btnSubmit_Click(Object sender, EventArgs e)
Server Name: VPS090

Next:
12/5/2011 2:23:26 PM Admin Alert Karin Schichtel Hackett Catholic Central Spirit Store
Error: : Object reference not set to an instance of an object.; ...
Error: : Object reference not set to an instance of an object.
Server Name: VPS090

Ideas?

I should add the customer shows up in the Customer list - Select doesn't show an order.

That's the problem, it's an erratic issue. Since then more orders with no problem, then we'll get one that goofs up. Even if we upgraded we wouldn't know for awhile and a series of orders. Whether customers are managing to do a routine that causes it or what we just don't know. I guess we'll just try to live with it.