One thing is though, when I subscribe up to this ISP, they asked me for my cable modem MAC ID.
I believe they didn't ask for cable modem MAC ID but your ethernet card MAC ID. Meaning you cannot change your ethernet card. You should use the assign MAC ID card only.

This is something I found from net:

If you have a Motorola CyberSurfr cable modem you will need to press the reset key on the back of the modem if you switch network cards. The ethernet card hardware address is read by the modem and once it is setup if the card is switched it must be reset.Just press the reset key for 10+ seconds and it will reread.
I have found that with the new system your NIC's MAC address must match what the cable system has. That is the Linux system you plug into the cable modem must use the same MAC that is programmed into the board.
If you didn't switch your network card (nic) then you could try this step:

1) Edit /etc/resov.conf
nameserver 202.137.3.120
nameserver 202.137.3.121

2) Edit /etc/network/interfaces
# /etc/network/interfaces -- configuration file for ifup(, ifdown(

# The loopback interface
# automatically added when upgrading
auto lo eth0
iface lo inet loopback


iface eth0 inet static
address 202.136.XXX.102
netmask 255.255.255.0
network 202.136.XXX.0
broadcast 202.136.XXX.255
gateway 202.136.9.1

3) Edit /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
MACADDR="*" *Your MAC ID
IPADDR=202.136.XXX.102
NETMASK=255.255.255.0
NETWORK= 202.136.XXX.0
BROADCAST=202.136.XXX.255
GATEWAY 202.136.9.1
ONBOOT=yes

4) In root shell run command:
/etc/init.d/networking restart
ifconfig -a

**Never quit **Take it as a challenge**That what makes me stay with Linux**