Ok donc j'ai vu le bug et je l'ai corrigé dans mon code
La ligne 148 de user.php dans admin est ainsi :
$db->exec("INSERT INTO tusers (firstname,lastname,password,salt,mail,phone,fax,company,address1,address2,zip,city,custom1,custom2,profile,login,chgpwd,skin,service,function) VALUES ($_POST[firstname],$_POST[lastname],'$_POST[password]','$salt',$_POST[mail],'$_POST[phone]',$_POST[fax],'$_POST[company]',$_POST[address1],$_POST[address2],$_POST[zip],$_POST[city],$_POST[custom1],$_POST[custom2],'$_POST[profile]',$_POST[login],'$_POST[chgpwd]','$_POST[skin]', '$_POST[service]', '$_POST[function]')");
il faut quelle soit ainsi :
$db->exec("INSERT INTO tusers (firstname,lastname,password,salt,mail,phone,fax,company,address1,address2,zip,city,custom1,custom2,profile,login,chgpwd,skin,service,function) VALUES ($_POST[firstname],$_POST[lastname],'$_POST[password]','$salt',$_POST[mail],'$_POST[phone]',$_POST[fax],'$_POST[company]',$_POST[address1],$_POST[address2],$_POST[zip],$_POST[city],$_POST[custom1],$_POST[custom2],'$_POST[profile]',$_POST[login],'$_POST[chgpwd]','$_POST[skin]', '$_POST[service]', $_POST[function])");
$_POST[function] est déjà quote plsu haut dans le code ce qui double les simple quote autour du champs et crée une erreur