Modem and XBL Problem

My modem is a Motorola 2210-02-1006 and I use a Linksys WRT600N. I have this problem where my modem just goes on and off at times for a short period of time, I kinda configured it a bit so it hasn't done it so far, but for some reason I cannot connect to some of my friends on xbox live, I can only connect to like two, and it's not them because I know they can play together with other friends on my list so it's just me left out. But There is also this other problem, I run a diagnostics test on my modem and everything passes except my IP, it fails. But none-the-less I'm surfing the interwebz and playing on xbox live with no friends to accompany me on owning newbs. =/ Any solutions? If you need more info just ask.

 

how have you "configured" the modem? What time of day does it normally drop out? How long are the outages?