Network disconnection problem

[aharpro26]

I just got a new cable modem, then got my old one back. DHCP and static users both get extreme lag (just about shuts off). Internet games lag you out and websites stop loading. This happens randomly, but doesn't happen that often. I run a CS:S server, and the users get like 900 pings out of the middle of nowhere. I have tried 3 different routers. 2 linksys and 1 netgear. all three did the exact same thing. i tried unplugging my cable modem for a long time then starting it back up, but that did not fix the problem. What could i do to fix this problem?

any help is appreciated
thanks