I've got a home network of Pcs sharing a broadband internet connection. A few days ago, the browsers on approximately half of them simply stopped working. Whatever pages we browse to, we get that oh-so-helpful 'page not found' error.
Here's the crazy part. Anti-virus updates and instant messengers, etc. connect just fine. We've got internet, but the browsers can't see it?
What is going on? Why is it affecting half of the computers suddenly? Most importantly, what do I do about it?

Hey there gmtyrant,

It sounds like the antivirus software/firewall might be preventing access to the internet, or some settings have been changed.

• Could you try disabling your antivirus and firewall (if you have one other than the windows one) and see if you can browse the net?
• Make sure you haven't installed any pop-up blockers, they can also be found on the toolbar, uninstall any additional toolbars you have.

Antivirus disabled. I'm using windows firewall. Pop-up blockers are a stupid waste of my CPU time. I don't have one. All extra toolbars are disabled.

As an extra bit of info, the computers are coming up clean on anti-virus and spyware checks.

Still nothing.

In your router settings, try opening port 80 (I have heard of problems such as this because the router wasn't redirecting port 80 correctly).

Port 80 is open, but when I checked that I found something else: All the working computers are using static IPs, all of the non-working computers are using auto-assigned IPs. Could that be it?
I will test that today if I get the chance.

Yes that is a possibility, just assign IP addresses to those other computers that aren't working.
Might be a good idea to check and see what other settings are enabled on the working machine e.g subnet mask, default gateway. If they are enabled just use those same numbers on the other machines.