Well, except for the fact that you're getting an 80... instead of the
81... that you were getting with the router, it all sounds OK.Hard to tell from the other side of the pond, try a hard reset (hold reset 30s, remove power, wait 30s, reconnect power, wait 30s, release reset) and without changing anything, setting a password, or doing a single bit of configuration, see if it works. Remember to power up the cable modem, the router, and the computer, in that order, waiting
60 seconds between devices.Then I'd try cloning the MAC address of the router to that of your computer, as many cable systems care about MAC address.
If neither of those work, and you didn't do anything else when it stopped working, I'd try another one.