Error "Duplicate entry"

Hi guys, I have a problem with Chronoform
I have created one form with the multi page method.
The first form_child is a sort of login form, where the user writes his name, surname and email address.
This three datas are already present in the database table, provided by an external server.
In the validation server side (of the first form_child) I have the code to validate the email (if the email is in the database table, the user goes to the next form_child, otherwise he goes to the registration page in the external server)

This is the codex:

<?php
$db =& JFactory::getDBO();
$email = JRequest::getString('mail_pay', '', 'post');
$query = "SELECT COUNT(*) FROM `#__chronoforms_abstract` WHERE `mail_pay` = '$email'; ";
$db->setQuery($query);
 $rec = $db->LoadResult();
if ( !$rec ) {
return "email non trovata";
}

?>

In the second form_child the user must insert a few other datas.
Once he has completed this procedure, after cliking the submit button, the following error message appears:

Tablechronoforms_abstract::store failed - Duplicate entry [email]'xxx@xxx.it[/email]' for key 'mail_pay'

how can I solve this problem?

Hi,
It would seem the JTable class created for your form does not keep track of keys correctly. Could you post a backup of your form, along with a description of your table layout?

/Fredrik