That sounds like a physical problem on your cable provider's end. Did this problem just suddenly start happening?
well, i just got back from my dad's, who has the same isp exept he has more bandwidth. He even has the same modem and router i have here and i had no problem at all. it just started when i got home 2 days ago. I called the company and the guy came out and looked at it and said send and receiving levels were really bad. so appearently he did something to fix it by moving my connection closer to the local tap. doesnt seem to fix anything.