Cheverge

I was having problems with my modem, I have comcast internet, and they tech told me to go exchange the modem for a new one at the local office. I did and they gave me a scientific atlantic, different brand than before. Everything worked fine before, now If i plug the modem straight into my pc it works fine, but when I try to go through the router it doesnt work wired or wireless, it reads cannot find server. I tried resetting the router etc and tried restting the router back to factory defaults and still doesnt work. please help. The router is a belkin F5D7231-4