Guys, thank you very much for you time and effort.
I've found the error looking in the apache logs as suggested by Frankb.
The error was saying "httpd: Could not reliably determine the server's fully qualified do...."
So I googled what to do and the answer was to edit the file /etc/sysconfig/network with those entries:
NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=HOSTNAMEOFTHESERVER
After that I reboot the server and all was good. Thanks very much!