Please review the firewall rules. DELETE them. YES, those rules of the firewall that comes with Windows Seven. DELETE them. Do you have more than one network connection? Delete the firewall rules for all network connections.

Then reboot and see if it autoupdates itself.

Review Avast main GUI → settings → updates → "Direct connection (no proxy). While you are there, select the checkbox that says “I am permanently connected to Internet”. Then Reboot.

Review again Avast main GUI → Maintenance → update and see if there are any errors and when was the last attempt to update. Do NOT force the updates.

Doesn’t work? Try to download the complete VPS http://www.avast.com/download-update. Run it and REBOOT (do not try to continue using the system after running the VPS. I need to reboot so the info is really updated correctly in the GUI).

Please report back.