Perplexing Internet Problem

I have been trying to figure this out for weeks now, and I'm hoping someone here can help me solve this problem I am having.

I am running a cable modem from Cox Communications on cat5 to a Linksys WRT54G router, which then connects to two desktops with cat5. As of about a month ago, I have been getting very high lag, and completely lagging out for 5 seconds at a time on programs like ventrilo and games. If I do not get disconnected, everything catches up very quickly, and then it will happen at a seemingly random time 5 seconds anywhere to a few minutes later, constantly.

My first thought was maybe my brother or I was uploading or downloading anything, and we are not. I assumed maybe someone was on the router, so I turned on the wireless mac filtering and check the clients list, and we are the only ones on. Thinking maybe the router is busted, I bought a new one and put it on the router, and got the same problem. I next replaced the cat5 between the router and cable modem. Bingo. For a while, the internet worked great, no problems, but then about a week ago they started up again.

Thinking now that it was the modem, I brought the modem upstairs, connected it to the axial socket in my room that my TV gets its cable from, and plugged it directly into my computer. The internet ran flawlessly. (This is not a one time occurance; i have brought the modem upstairs a few times now and every time it has run great; I do not think it's the internet provider or modem) Convinced it was the cat5 between the modem and router, I replaced that, as well as the cat5 going from the computers to the router. Still lag.

The only thing I can even fathom it being now is the axial socket. When brought upstairs and plugged directly into the computer, it runs very well.

On a more different note, while pinging the DNS, I receive on average anywhere between 6-12% loss.

The cable modem should be the only thing on the line. That line should come off the first splitter in the house. You also might have COX check the signal strength. Too many tvs can drain the signal.

Bump ~_~