[CentOS] [CEntOS] - problem with iptables

hi all,

I have a problem with iptables on CentOS 6.2.
I configured:

chkconfig iptables on
and the file /etc/sysconfig/iptables

if you reboot the machine configurations are not loaded.
iptables-L gives me the default configurations (not assigned)
if I (a machine booted): service iptables start then then it works.

how can I fix?
thanks in advance