The web shield has nothing to do with the updates so I don't know what is going on.
Or if you are saying aside from not being able to update, you can't browse ?
If that is correct then this is indicative of your firewall blocking avast.
What is your operating system ?
What is your firewall ?
Does it allow avast.setup & avastSvc.exe internet access ?
- If it does delete the entry for it and do a manual update and reconnect to the internet, this should force the firewall to ask permission again.