Problem with Symfony 2

I try to use symfony 2 but when you press some link in the configuration, in http://127.0.0.1/symfony/web/config.php the error: Call to undefined method Symfony\\Component\\ClassLoader\\UniversalClassLoader::registerNamespaces() cames up... I can't use symfony and there is no answers in google that let me see what is the problem.. please any help ??