What is your firewall ?
Does it allow avast.setup internet access ?
If it does delete the entry for it and do a manual update and reconnect to the internet, this will force the firewall to ask permission again.
Can you do a manual Update?
right click the avast ‘a’ icon, select Updating, iAVS Update.
Re the repair of avast.
Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button and scroll down to Repair, click next and follow.
Personally I don’t think it will have any effect.
Please, post the last 200-250 lines of avast log: C:\Program Files\Alwil Software\Avast4\DATA\log\Setup.log
Also check:
If your subscription allows the update right now (i.e., if it is not expired). Home (free) version need registering each 14 months.
If your firewall settings and allow avast.setup to connect.
If you’re not sure, just turn off your firewall (to be sure the update failure is not due to it).
Maybe you should ‘remove’ avast.setup entry, try to update, receiving a new alert from the firewall, allowing it and checking it to remember.
Check your proxy settings into avast!:
Left click the avast icon > Settings
Update (Basic) > Details > Proxy
Make sure your browser is not set to “Work Offline” (this option is generally in the File menu).
If it doesn’t help, try switching from “Auto-detect” to “No proxy” (I’m assuming you’re not connecting to the Internet via proxy).