Cable Modem connected to router: Slow Speed

[easygoing]

Hi.

I've got a surfboard cable modem that works fine when it's directly connected to the computer, but when I connect it to my DLink router, it works fine for about a half hour and then starts going rather slow. What I mean is that browser and download speeds are incredibly slow.

And when I'm playing the online game World of Warcraft, the game will play fine for a half hour or so, and then all of a sudden will start lagging. The latency bar will show up blood red and I have to wait an annoying number of seconds to interact with anything.

Funny thing is that when I release and renew the ip adress of my router, my internet works fine--again, for about a half hour. I've tried all the tricks. Comcast tells me to unplug my modem, wait fifteen seconds and plug it in again, but that's only as good as releasing and renewing my ip address.

If anyone has beaten this problem, or has a solution for me besides the actions I've taken, I'm all ears.

I have heard of the trick of replacing the MAC address of my router with that of an old network card, but I don't have one to spare, and wouldn't know how to change my routers MAC proprely if i did.