I think to account for this error you would place this on the top of your failure page (if it isn't already there):
<?php
require_once("WA_eCart/Adv_CO_Scripts/PP_ECO_Process_PHP.php");
?>
Then add this code to trap the error and show a specific message:
<?php
if (PP_ECO_Process_Result("Error Code") == "10486") {
?>
<p>
Your purchase has been declined.<br>
Possible reasons for payment failure include:<br><br>
The billing address associated with the financial Instrument could not be confirmed.<br>
The transaction exceeds the card limit.<br>
The transaction was denied by the card issuer.<br><br>
Please <a href="checkout.php">try again</a> and use a different payment method.
</p>
<?php
}
?>