I have two computers. One

Question

I have two computers. One is w/ a wireless router. Mine which is the second computer keeps connecting and disconnecting. I had determine that it was the router so I put in a new one. Ir seem to help for alittle while and then I started having problems again. I noticed if you unplug the cable modem it takes a very long time to reboot and I mean a long time. I am beginning to wonder if the cable modem needs to be replace. On the computer w/ the router/modem set up there isn't any connection problems. Thanks