Solutions: Yes this is known bug caused by the middle name attribute in recent versions of Magento. Here is the solution for this issue, we need to insert records for middle name attribute for old customers, here is the script to update database table

require 'app/Mage.php';
Mage::app('default');

$db_read = Mage::getSingleton('core/resource')->getConnection('core_read');
$tablePrefix = (string) Mage::getConfig()->getTablePrefix();

$sql = 'SELECT entity_id FROM ' . $tablePrefix .'customer_entity where entity_id NOT IN (SELECT entity_id FROM '. $tablePrefix.'customer_entity_varchar where attribute_id = 6)';

$db_write1= Mage::getSingleton('core/resource')->getConnection('core_write');
$value=$db_read->query($sql);
echo "<br>Total: ".count($value);
$i =1;
while ($row = $value->fetch())
{
    //print_r($row);
    echo "<br>".$i." - ".$row['entity_id'];
    $sql = 'INSERT INTO '. $tablePrefix.'customer_entity_varchar (entity_type_id, attribute_id, entity_id) VALUES (1, 6, '.$row['entity_id'].' )';
    $db_write1->query($sql);  
};