Magento – Customers Unable to Register on Frontend

At last found the problem, there was a custom modification, which didn't throw an exception, when already registered customer tries to register again. So, that customer was considered as a Guest [NOT LOGGED IN] customer.

The bad part is that, it was straight away done in core files, so I didn't find it until now.

I didn't want to mess up with these changes, so created an event-observer to automatically login, if the customer is already registered.

if(!Mage::helper('customer')->isLoggedIn()){
    $data = $evt->getEvent()->getControllerAction()->getRequest()->getPost('billing', array());
    $customer = Mage::getModel("customer/customer");    
    $email = $data['email']; //email entered in billing address section
    $customer->setWebsiteId(Mage::app()->getStore()->getWebsiteId())->loadByEmail($email);

    if($customer->getId()){
        Mage::getSingleton('customer/session')->loginById($customer->getId());
    }
}

I'd say that you need to change your XML like this:

<global>
    <fieldsets>
        <checkout_onepage_quote>
            <new_attribute>
                <to_customer>*</to_customer>
            </new_attribute>
        </checkout_onepage_quote>
        <customer_account>
            <new_attribute>
                <to_quote>*</to_quote>
            </new_attribute>
        </customer_account>
    </fieldsets>
</global>

And also - add the field to the quote in your setup file like this:

$installer = $this;
$installer->startSetup();

$connection = $installer->getConnection();
$quote_table_name = $installer->getTable('sales/quote');
$connection->addColumn($quote_table_name, 'new_attribute', array(
    'type' => Varien_Db_Ddl_Table::TYPE_TEXT,
    'length' => 255,
    'nullable' => false,
    'comment' => 'New Attribute',
));

$installer->endSetup();

(You can, of course use the alter table call, but I like this method better.)

Magento is first copying the fields from your request to the quote and then it's copying them back to the customer when the customer is being created.

Also, be sure that you have your new attribute ("new_attribute" in the example above) in the customer_form_attribute table for the checkout_register form_code

Hope that helps.