What garrettp told you should take care of all that unless you have another firewall script pre-installed somewhere that is resetting iptables such as APF, CSF, or some other (a couple of data centers have their own proprietary scripts).
The "iptables -F" temporarily flushes iptables
The "rm -f -- /etc/sysconfig/iptables" removes the entries permanently
Don't forget to restart "service iptables restart ; service cpanel restart"
If you reboot and get the blocks back then you got something else going on and I would say you have some other firewall script active or you are on an old traditional VPS server (Eeeewww!

) and they got you setup to load a standard image at each boot. In the later case, your only recourse outside of moving would be to setup a script to auto make the changes you need after each reboot.
You can always disable iptables temporarily till you finish getting Cpanel installed which incidentally is a whole lot more than just simply running
http://layer1.cpanel.net/latest which would be only about 1% of what all you need to do to get Cpanel up and running properly.
Regarding what I just said:
Code:
service iptables stop
chkconfig iptables off
(NOTE: I absolutely do not recommend that be used for anything permanent!)