Orders Not Sent For Payment...

I got an email from a customer this week who said they made an order, was never sent to pay, but the system marked the order as paid. The amount due was greater than $0. I can't see why it would happen.

I did a query between the orders table and the paypal table for any orders that did not have associated paypal payments. We only accept payment by paypal, so every order should have an entry.

57 of our over 19,000 orders did not get paid for. $160 in value not billed for this year.

Has anyone else seen this? Any ideas why this happens?

In Admin->Modules->Payment, you have several payment modules available. Have you edited any of them and changed "Enabled?" to false, instead of just clicking "Remove" to properly prevent them from being used?
Also, for those orders that you allege didn't collect payment, which payment module does your store show was used for the order? Admin->Customers->Orders-> 2nd column shows payment and shipping module used.

Also, click "Reply" below and include the answers to the "Posting Tips" questions when you answer the above questions.