Do you run any iptables script ?
Also it may be a setting in /etc/apache/httpd.conf that deny access or an .htaccess file in the directory that contains index.php. Did you look at your error log file ?
try : tail -f /var/log/apache/error_log , and try to access to the web server with the other machine, then look in the log.
If your index.php is in /home/www/ directory for example , try add to httpd.conf (if there are no directive for /home/www) :
<Directory "/home/www">
AllowOverride None
Order allow,deny
Allow from all
</Directory>
[edit]
Great, it is fixed
But it is weird that it does not listen the port 80, what have you for Listen directive in httpd.conf ?