How are the two routers connected to the Cable Broadband service? If you have connected a Network Switch to the Cable Modem's ethernet port and are then connecting two routers to that, it isn't going to work. That would have the same effect as connecting two computers to the modem - the ISP only allocates one IP address which will go to the first computer (or router) to connect and the second won't have internet access.
You would have to connect the second router to one of the first router's LAN ports so that its WAN IP address was actually a LAN address allocated by the first router. The routers would also have to allocate LAN IP addresses in different subnets (address ranges) or there would be IP address conflicts.