Firewall does not work since last update

Since the update of Windows Vista and Avast, appr. 1 week ago, my firewall does not work anymore and I also can’t start it manually. Any suggestions of what I should do?

Repair Avast:

  1. Control Panel → Add/Remove programs → Avast
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.