Internet works, browsers do not

I have a fairly curious problem, and I'm not sure there's an answer for it.

I'm running Windows Vista Home Basic, and randomly my internet browsers just totally stop trying to connect and just spit out error messages, but everything else still works (usually). MSN, Steam, my antivirus updates on time, everything that isn't HTTP pretty much. The internet browsers will last anywhere from 5 minutes to 24 hours before keeling over.

I've done a pretty thorough Google search on this and I'm at least not alone, but in another sense I am...

A lot of people have said "oh I disabled/uninstalled ZoneAlarm or Bitdefender or so and so a program and it worked" but I don't run those. Never have had ZA or anything on my computer.

The only program I have in common with the most common ones is Spybot S&D, and I disabled that on startup and sure enough, didn't work.

I do not have any Vista service packs, I don't think. Nothing explicitly called that anyway. I have a bunch of updates that I installed when I got the computer, so I can't uninstall SP1 to fix it since I don't think I even have it.

Is it a process running that can cause this?

I'll bet I am in this for the long haul, aren't I...

edit: I should clarify this started a week or so ago. Nothing changed in that time. It was working fine, and then it wasn't.

This is a strange one....

Which browser do you mainly use? have you tried another browser?

I use Firefox 3.5 but the problem started before that, about a week ago. Once it stops working, Internet Explorer stops too, all HTTP seems to just keel over and die, but everything else still works like Steam and MSN. Just google "internet browser stops working windows Vista" and you'll see what I'm talking about. Problem is a lot of those people solved it by uninstalling programs I've never had on here before. The only thing that brings back the HTTP functionality is a reboot, nothing else helps at all.

edit: More information - People have also said "I scanned my system with Malwarebytes and it found something, I removed it and that fixed it" so I tried that too.... no infection. Used Avira Antivir to do a virus scan, no infection.

are your network card drivers up to date? have you checked with your isp to see if they have changed anything? i started losing my connection every day at 12pm. i called my isp and found out they were upgrading the lines in my area to fiber optic.

They haven't changed anything. Perhaps I will remember everything soon enough, but I sort of neglected to mention that there are two other computers on the same connection and they have no problems. One runs Windows XP and one runs Windows 2000. I'm the only one with the problem and I run Vista. All my other research on this has led me to believe it's mainly a problem that only affects Vista users. (some XP users are affected but not many.)

Also we're sort of splitting the connection and my ISP sort of wouldn't appreciate that, so we sort of can't call them about it...

If web browsing is the only thing affected, that would lead me to believe the problem lies in your DNS settings. You could try using the OpenDNS servers for a couple days and see if the problem persists

OpenDNS Servers:
208.67.222.222
208.67.220.220

I love the irony. I was typing a reply, I went to post it, and it wouldn't load and I had to reboot.

What I was saying was, I haven't changed anything so how would the DNS settings all of a sudden start causing problems after seven months of operation? And what would I do with those IP addresses?

edit: Alright, fingers crossed. It's been 24 hours and no reboot needed yet.

All I've done in that time was:

-Install SuperAntiSpyware free version and run a scan. It found four tracking cookies and that is it, so I removed them.

-Installed a file shredder program to replace the one I would lose when I...

-uninstalled Spybot S&D.

Spybot S&D the culprit? I had it disabled on startup... could the TeaTimer.exe have been doing something bad?

That's all I've changed, and it hasn't mucked up on me. You know, yet.

edit 2: Yeah, figures, it just happened again.