After ordering, a customer's address is lost

[dremhmrk2]

We have been noticing that intermittantly, when a customer checks out, somewhere in the process their shipping address gets scrubbed from the database. We believe this happens after the order has been "completed" because we recieve a proper order confirmation which contains the address. However going back into their account info from our back-end, we can see that the address has been lost.

 

This has been happening to long-time repeat customers and new customers as well.

 

We are using the One Page Checkout add-on.

 

I need to know where to begin to look. Thanks guys!