I agree with fenderman, it's highly likely that when you got a new cable modem from your cable company, you were also assigned a new Public IP address. Furthermore, if your cable modem also acts as your router, you will need to login and reconfigure the port forwarding.
i am still using the router i have always had when the modem was changed i did receive a new external ip address but ever since the switch i can not connect to my internal server