upgrade/downgrade products does not work

[suprahost]

With 3.5.1 I am receiving this error when a client try to downgrade/upgrade a product

 

Fatal error: Smarty error: [in orderforms/boxes/order-complete.tpl line 41]: syntax error: unrecognized tag: bdv_protocol="https://"; (Smarty_Compiler.class.php, line 439) in /home/user/public_html/whmcs/libs/Smarty.class.php on line 1095

 

Any help please ?

 

orderforms/boxes/order-complete.tpl contains this

<p><b> » {$LANG.orderconfirmation}</b></p>

<p>{$LANG.orderreceived}</p>

<blockquote>
 <p>{$LANG.ordernumberis} {$ordernumber}</p>
</blockquote>

<p>{$LANG.orderfinalinstructions}</p>

{if $invoiceid}<p align="center"><a href="viewinvoice.php?id={$invoiceid}" target="_blank">{$LANG.invoicenumber}{$invoiceid}</a></p>{/if}

<p align="center"><a href="clientarea.php">{$LANG.ordergotoclientarea}</a></p>

 

Thanks