Web surfing access periodically dropping out

[YakooMarkTwo]

I'm running Windows XP Pro, Zonealarm, Norton AV 2005, Firefox 1.0.1. I use Roadrunner cable internet. Just recently I've developed a problem where my internet surfing won't work. every 20 minutes or so, Firefox (and IE also) just won't connect to any websites. They time out. But AIM and my P2P programs still work. The only thing I've figured out is that I can wait 20 minutes or so and it will come back up, OR i can unplug my cable modem and reset it to get access again (needless to say, very annoying).

I run Spybot, HiJackThis!, Adaware, CWShredder, and they don't really find anything.... every once in a while they do, but they seem to delete it fine. I did have a CoolWebSearch infestation that I believe I cleared up, but that was months ago and this new problem is very recent.

Is there any thing I can do to test if my IP address is problematic? Is it my web surfing port (like I said, messaging and P2P still work all the time)? I tried to contact my ISP, but the "don't support Firefox" and wouldn't help me.

[PCguy]

It sounds like you have a DNS issue, which is probably coming from your ISP. Tell me how you have your PC connected to the internet. Is it directly to the cable modem or is it through a router?

[YakooMarkTwo]

I connect to the internet directly through a modem - no router. friends of mine who use the same ISP told me about something similar happening to them. They called Roadrunner and were told that they (RR) had changed something - which I can't recall what - and relied on customers not being able to use their services and calling in for help SO THAT ROADRUNNER WOULD KNOW EXACTLY WHO THAT CHANGE HAD AFFECTED. Seems like a jerk thing to do, and i'm not sure that my situation applies.

sorry for the lenghty rant.