Do you have any other firewall software installed?

First, try a repair:

  • Go to Control Panel>Programs.
  • Select avast! Internet Security.
  • Scroll down to where it says Repair. Select it and click next.
  • Reboot.

If that doesn’t work try a clean install:

  • Download the latest version of AIS here
  • Download the avast! Uninstall Utility here
  • Reboot your PC
  • Uninstall avast! in Control Panel>Programs. Reboot.
  • Start up in Safe mode. Run the uninstall utiity. Reboot.
  • Reinstall avast.