Problema al configurar Symfony 2

[Enano_la22]

Hola a todos, estoy tratando de configurar Symfony2 en una maquina y me es imposible. Ya lo hice en otra y funciona lo mas bien, pero en esta maquina no me funciona.
El tema es el siguiente, cuando pongo : http://localhost/Symfony/web/app_dev.php

Aparece la pagina de inicio, todo bien., la que dice:
Welcome!

Congratulations! You have successfully installed a new Symfony application.

Quick tour Configure your appication Demo
Read the Quick Tour(Boton) Configure (boton) Run The Demo(boton)

Luego, quiero ejecutar el Demo, presiono en el boton Run The Demo y me sale el siguiente error:

Not Found

The requested URL /Symfony/web/app_dev.php/demo/ was not found on this server.
Apache/2.2.20 (Ubuntu) Server at localhost Port 80

Que yo sepa no hice nada distinto a lo que hice en la otra maquina.
Gracias por su ayuda!

[masterpuppet]

Haz comprobado que el servidor cumpla al menos los requisitos mínimos ?

Saludos.

[Enano_la22]

Hola, Gracias por responder. Si cumple con los requisitos:
al ejecutar el comando php app/check.php

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20090626+lfs/sqlite.so' - /usr/lib/php5/20090626+lfs/sqlite.so: cannot open shared object file: No such file or directory in Unknown on line 0
********************************
* *
* Symfony requirements check *
* *
********************************

php.ini used by PHP: /etc/php5/cli/php.ini

** WARNING **
* The PHP CLI can use a different php.ini file
* than the one used with your web server.
* If this is the case, please ALSO launch this
* utility from your web server.
** WARNING **

** Mandatory requirements **

OK Checking that PHP version is at least 5.3.2 (5.3.6-13ubuntu3.2 installed)
OK Checking that the "date.timezone" setting is set
OK Checking that app/cache/ directory is writable
OK Checking that the app/logs/ directory is writable
OK Checking that the json_encode() is available
OK Checking that the SQLite3 or PDO_SQLite extension is available
OK Checking that the session_start() is available
OK Checking that the ctype_alpha() is available
OK Checking that the token_get_all() is available
OK Checking that the APC version is at least 3.0.17

** Optional checks **

OK Checking that the PHP-XML module is installed
OK Checking that the token_get_all() function is available
OK Checking that the mb_strlen() function is available
OK Checking that the iconv() function is available
OK Checking that the utf8_decode() is available
OK Checking that the posix_isatty() is available
OK Checking that the intl extension is available
OK Checking that the intl ICU version is at least 4+
OK Checking that a PHP accelerator is installed
OK Checking that php.ini has short_open_tag set to off
OK Checking that php.ini has magic_quotes_gpc set to off
OK Checking that php.ini has register_globals set to off
OK Checking that php.ini has session.auto_start set to off

** Optional checks (Doctrine) **

OK Checking that PDO is installed
OK Checking that PDO has some drivers installed: sqlite

Creo q esta todo bien.... nose que puede ser??

[GatorV]

¿Haz verificado si el servidor web tiene mod_rewrite instalado?

[Enano_la22]

Gracias GatorV, como hago para comprobar si esta instalado?hay algun comando? Gracias!

[GatorV]

Lo puedes verificar en tu httpd.conf, suponiendo que usas Apache, ¿Que Servidor Web usas?

[Enano_la22]

SI uso Apache. gracias GatorV. me voy a poner a revisar eso