Just for help other ppl who may pass the same.
I noticed the Bandwidth monitoring has been suddenly stopped.
I couldn't enable it again (ip_conntrack_netbios_ns module FAILED)
I found the solution in a Linode.com CentOS config guide:
nano /etc/sysconfig/iptables-config
edit:
IPTABLES_MODULES="ip_conntrack_netbios_ns"
to:
IPTABLES_MDULES=""
(save pressing ctrl+X, then Y for save, and Enter to confirm)
then run:
/etc/init.d/iptables restart
If you still have problems, open iptables-config again and edit:
IPTABLES_MODULES_UNLOAD="yes"
to:
IPTABLES_MODULES_UNLOAD="no"
(again, ctrl+X, then Y and Enter)
/etc/init.d/iptables restart
Done!