Hello Peter,
Thank you for your question about using a PO Box. Some sellers to not ship to PO Boxes, and they configure their account at eBay where the registered account is a PO Box. We can't turn it off, as it is set by the seller.
Unfortunately, we don't know about the situation until we place the bid for you, at which point eBay reports the error to us, which we report to you.
I hope this has been resolved to your satisfaction. If you have additional questions, please don't hesitate to ask.
bidslammer