Hi again,
you can go to troubleshooting section in avast setting, disable self defense, than stop all shields, e.g. by right clicking the avast icon, choosing avast! Shields Control - Disable for 1 Hour.
Then you may stop "avast! Antivirus service" from services control panel, or might even skip this step and kill avastsvc.exe, avastui.exe and avast.setup processes in task manager - if they are running.
No, go to your firewall, remove all notices of avast from the list of applications and then start avastui.exe from the avast installation folder again. Click, "Fix now" button to restart the service. You should see a popup from the firewall, as the serviceses are being started and accessing the net. If not, the firewall is not detecting/allowing network traffic correctly.
Lukas.