Intermittent latency to modem

I posted an initial question regarding this very same topic, but it didn't solved: http://forums.cox.com/forum_home/internet_forum/f/5/t/9005.aspx

The initial post was regarding a Ubee modem. I have since went to the COX store and switched out for a Netgear modem. Same deal, it's a modem/router/wifi combo. Works great, except when it doesn't.

I have posted a side-by-side terminal screenshot below. The first window is cox.net, second is the router, third is my local synology.

https://dl.dropboxusercontent.com/u/41660619/misc/cox_latency.png

I have intermittent packet loss and latency spikes when I am outbound through the router. It's probably every 30 to 60 seconds. Enough to screw up my iMessage delivery/read notes on my phone. Enough to upset my AT&T mobile cell to the point where it thinks it has lost a connection to the internet and has to reconnect (which drops my cell service at home).

I am connected to my networking with gigabit ethernet. I can ping all my local computers without packet loss 100% of the time. However, I get the packet loss and latency spikes of a very upset server. And it's only when I ping my router, or try to exit outbound. I can visually see when it happens if I'm browsing, or on IRC, because everything completely stops for a couple seconds.

What have I done to test? Remember, this is not a wifi issue at all, so I'm trying to avoid that all together. I have pulled up several terminals side-by-side, one to ping the modem, the others to ping my synology, and my macmini. Even when my pings are going through to the synology and macmini, the router drops packets and I get a spike between 1400ms and 3000ms. After that initial high latency, it drops down to maybe 1500, then 800, then 400, then back to normal. Roughly 30-60 seconds after, I get it again.

I know nothing about COX, nor the modems they use. Whether or not they have custom firmware on the modems. I do know that I did not have this problem until I moved houses and got COX. I had my macmini, my synology, my same exact cisco 8-port gigabit switch. Nothing has changed except the modem(s), and I see no latency/spikes until I'm outbound to the modem.

Any suggestions? Thanks!

Sean