avast free and Pro does not have a firewall…so what version have you installed ?
have you tried avast repair and reboot
For a repair of avast. Windows, Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.
Uninstall avast from Control Panel (if possible). If, for any reason, you can’t run it, try booting in Safe Mode and doing it from there. Anyway, boot after that.
Run the avast! Uninstall Utility saved on 1. If, for any reason, you can’t run it, try booting in Safe Mode and doing it from there. Anyway, boot after you’ve run it.
Install avast! using the setup saved on 2. Boot.
Register your free copy or add the license key for Pro. Or even upgrade your key from old versions.
Check and post the results. If, for any reason, you did not solve, try doing the step 3 in Safe Mode anyway.
I had responded to an invitation to try Internet Security and then when it expired uninstalled it and reinstalled Avast Free, being careful at each point to re-boot.
Responding to your advice, I looked but couldn’t find the Avast uninstall utility on the download page and didn’t scroll down far enough to see it on the Support page. So uninstalled Avast Free, re-booted, installed a new Avast Free and re-booted. But the System > Components > Problem Devices still reported missing drivers for Avast Firewall–apparently from the Internet Security trial.
Went back and found the uninstall utility and applied it following the steps you listed and the System message about missing drivers disappeared. It was not necessary to boot into safe mode at any time. I’m sure you haven’t missed the idea that it would be better for sales of Internet Security if stuff were not left behind and much more easily fixed if the uninstall utility were included in the trial package or at least given a more prominent place on the main Download page.