Router conflict with Roadrunner and/or their motorola modem

Question

I have owned a linksys router for over five years now and about 1 month ago my entire house comprised of 3 desktops one of which is wired directly to the router others are wireless, 4 laptops (wireless), 3 iphones, an xbox 360 (wireless), a ps3 (wireless), (i dont mean to flaunt but i stress the importance of a stable internet connection in a house of my size and), started hitting pings of over 2400's... there is connection but virtually no response....most sites time out before comeing up. so naturally we trouble shooted this anomaly on our own... tried connecting a computer directly to the motorola cable modem and found it in perfect working order... when on speedtest.net we saw pings around 15-20 and download speeds up to 19mbps every so often up to 25mbps but never lower. through either router new or old i see pings over 2400 with out fail and downloads areound 4mbps wihjch wouldnt be horrible if it werent for the latency.
so we figure old rounter.... got a new one. one of the linksys wrt110's and saw no improvement which was frusterating because the router was clearly the problem
so we thought for some reason the protocols within the modem itself were the problem and replaces this as well.... i have tested the signal power/strengths/frequencys with the modems as well and although my knowledge is limited to what i have learned on my own i know its well within proper ranges to function.  (it would be common sense id think seeing as how the signal is fine when not being filtered through the routers.but i tested anyway).
now i tried one other thing..and that was to instead connect the internet through my computer and thenback out into the router via a 2 ethernet cablescards andashared connection ... still no dice seeing as the internet connection was still giveing ping readings around 240. as a final resort to find whether it was routing in general that was conflicting or just the linksys routers fault for the latancy problem i connected another machine directly tomy computer via shared connection andit works perfectly but it isnt really a viable solution considering the multitude of internet hungary machines in my home.
now i know all this is rather vague but the story itself tells volumes about my problem but not really how to fix it... the only equally vague solutions i can conjure is to either 1. buy adifferant brand router ( i am rather attached to linksys afterthis length of time) or 2. find an underlying protocol or signal differance that wasnt there for almost5 year up till 1month ago. HELP me  please i just plain dont know enoughabout this and apearantly niether do many other people because i have talked with 2 linksys routertechs on phone and had timewarner cable come to my house twice aswell.. they even replaced the modem
im plain out of ideas

Answer 1

If i m not wrrong, you have connected your Router to your computer and your computer to the Modem and you have shared the Internet Connection through your Computer.
Well basically you dont have to share Internet connection from your Computer, As you Router already has a NAT and it can Share the Internet connections on your other computers also. 
Connect the Modem to Linksys router on Internet Port and Then connect your Computer to any available Ethernet Ports. Now you can configure your Linksys Router. 
If your Internet Service Providor is Cable follow this link
If your Internet Service Providor is DSL follow this link