|"firewall is taking the ip address of the cable modem"|
So what you mean is the cable modem is giving the firewalls wan port an ip address. That means the wan port is set to dhcp and the modem or a device beyond is suppling an ip address [dhcp server]
"the ip address of the firewall states is: 192.168.0.1 (which is the cable modem) but the real IP address i can see is on the cable modem."
What do you mean by "real" ip address on the cable modem?
192.168.0.1 is usually the LAN subnet [that is the side of the router the switch/pcs connect to]
ISP supplied static ips usually cost you more per month than the standard package. Have you talked to NTL about the static ip assignment on the wan interface of your router?
What exactly do you mean by internet stops working?
Can you ping the router lan and wan ips? Yahoo.com? Where in the chain is the break?