Failed user login on production server using Symfony framework (Authentication request could not be processed due to...)

Question

I'am using Symfony for a project and I have been trying to get the login to work on production server with no success for the past 2 days. I keep getting the error

Authentication request could not be processed due to a system problem.

I have followed the guide here (http://symfony.com/doc/current/cookbook/security/entity_provider.html) to setup loading users from database.

My security.yml file:

security:
encoders:
    Symfony\Component\Security\Core\User\User: plaintext
    Acceptme\UserBundle\Entity\User: plaintext
role_hierarchy:
    ROLE_SUPER_ADMIN:   [ROLE_ADMIN, ROLE_ALLOWED_TO_SWITCH]

providers:
    in_memory:
        memory:
            users:
                patricia:
                    password: patricia
                    roles: 'ROLE_ADMIN'
    users:
        name: user_provider
        entity: { class: AcceptmeUserBundle:User, property: username }

firewalls:
    user_area:
        pattern: ^/
        anonymous: ~
        provider: user_provider
        form_login:
            login_path: login_route
            check_path: _login_check
            default_target_path: homepage
    dev:
        pattern: ^/(_(profiler|wdt|error)|css|images|js)/
        security: false

    default:
                anonymous: ~
                http_basic: ~

access_control:
        - { path: ^/admin, roles: ROLE_ADMIN }

My SecurityController.php:

namespace AppBundle\Controller;

use Symfony\Component\HttpFoundation\Request;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Security;
use Symfony\Component\Security\Core\SecurityContext;

class SecurityController extends Controller
{
/**
 * @Route("/login", name="login_route")
 * @Template("security/login.html.twig")
 */
public function loginAction(Request $request)
{
    if ($request->attributes->has(SecurityContext::AUTHENTICATION_ERROR)) {
        $error = $request->attributes->get(SecurityContext::AUTHENTICATION_ERROR);
    } else {
        $error = $request->getSession()->get(SecurityContext::AUTHENTICATION_ERROR);
    }

    return array(
        'last_username' => $request->getSession()->get(SecurityContext::LAST_USERNAME),
        'error'         => $error,
    );
}

/**
 * @Route("/login_check", name="_login_check")
 */
public function securityCheckAction()
{
    // this controller will not be executed,
    // as the route is handled by the Security system
}
}

I have tried uploading the project on 2 different web hosts (FatCow & GoDaddy) and the problem remains. Locally i am using PHP 5.4.19 (FatCow uses 5.3.2 and GoDaddy uses 5.4.37). Keep in mind that when working on localhost with XAMPP everything works fine!

I've confirmed that PDO is enabled in both cases. I've confirmed that the database username, password and host are correct in the parameters.yml file. Error logs on both local and remote servers show nothing.

I have followed all directions from this previous post Deploying Symfony2 app getting fosuserbundle errors and still no success.

I appreciate all the help in advance.