I need help with my router/modem?

I have gone through three routers in the last six months. The first was one from Net Gear which stopped connecting to the internet. The second was a Belkin, which worked initially, then there was no connection to the internet. The third was a new Belkin, which never connected. The problem is not the wireless aspect, but that the router makes no connection with the modem. I have set, reset, installed and reinstalled every way possible. Belkin keeps sending the same directions to reset. Comcast (my internet provider) keeps telling me the modem works fine and it's the router. I am at a total loss. Ideas?