i have had comcast internet for over 3 years and i have never had a problem connecting to live through my router( I have the x-box connected to the router through 2 additional 6 port switches daisy-chained) i only have one ip address and it is seamless.
Try setting you internet connection settings in your router to dynamic ,and your DNS server to auto that may help.
I hope this can save u a couple bucks a month
