You didn't answer the firewall question ?
Some firewalls when disabled block outbound access so that could also be an issue.
If we can rule out the firewall then there are other things which can be checked.
As to will a clean reinstall in the order listed resolve it for you, I don't know for certain. What I do know is if you don't try it 'you' will never know.
Actually I answered that my firewall is disabled (post #4). I've had the firewall disabled while still running avast v.4, and I didn't have any problems connecting to the web, until I installed v.5 because I kept getting a pop-up message that my v.4 subscription was about to expire on April 1. So I went ahead and downloaded v.5, and installed it (the installation automatically removed v.4).
After rebooting, I was pleased with the new interface, but when I opened my browser (Opera 10), I couldn't connect to the web. At first, I thought it was Opera's fault, so I tried Firefox...and same result....no internet connection.
After a little head scratching on my part, I right clicked the avast icon, saw the avast! shield control and the options to disable. I clicked the disable for 10 minutes, and surprise, I got internet connection once again in Opera and Firefox.
But after 10 minutes, when shield control became active again, I lost my web connection.
Now, I have Web Shield permanently disabled but the other controls still active...
There was a reply also posted to this thread by Logos that other users are having the same problem, so I'm wondering if this is a software bug that has to be fixed by avast tech support.
Thanks for your patience. I'd really like to stick with v.5 and have Web Shield running too. Btw, my OS is WinXP, SP3.