SP1 Networking problem

I have installed [4/5/2011] Windows 7 SP1 final (via windows update) on an Acer

Aspire 1410-8414 notebook, with Windows 7 home premium installed.

Now no browser [IE, FF or Chrome] will load any website. The computer

connects to the internet, and media players will open streaming net

radio and tv stations without a problem, and program updating works

too; so it is just a browser issue.

The strange thing is that the embeded web browser within Winamp does

function properly, so only stand-alone browsers won't load.

What I have done:
1] In Control Pannel>AdminTools>Services: computer browser and all
relevant IP services are started and running properly.

2] In PC Tools firewall: unrestricted in/out privilages are allowed for
all 3 browsers, and network status is "active".

3] There is no apparent conflict with Avast6 web or network shields.

4] I have reset/refreshed: winsock,ipv4,ipv6 and flushed dns.

I can't think of anything else to do. I don't want to have to

uninstall SP1 to be able to get online. Any ideas? Thanks.

It did turn out to be an SP1 conflict with Avast6's network shield. I'm working with their tech support to keep Avast on my system. (I really do like it better than any other antivirus.)
But, maybe you're right and I'll have to get rid of it.