Hmm this is tough ... and yes by Lan cable I mean the cat-5 cable :p Also I am not familiar with your ISP.
- The modem is connected to the Router?
- Are the modem lights blinking correctly?
I have a router / modem all in one type device, so thats why i said connect to the modem :p ... but before this, I had 2 separate devices, modem + seperate router. I remember connecting my pc to the router via cat-5, and then going to the router's config page to set up the login/password and ip gateway to the ISP. You should use "bridge mode".
Also the security settings on the router may be set to not allow connections for mac addresses not in its list? Can other laptops connect to router via cat-5, can they get on the local network that way? If youc can do wired connection and just not WiFi, then it must be the WiFi settings area/ISP connection area that needs work.
There should be nothing in the modem specifically stamped with your account info that you can't just re-enter manually, I remember resetting the modem countless times when I was learning how to set it up lol, it did nothing at all, it was the settings in the router.
You should call or visit the ISP's website/call center, they usually have a troubleshooting walk through for Lan setup.