Your SP1 update may have messed with the settings - Try a repair of avast:
Win7 - Control Panel, Programs & Features, uninstall a program, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
If that doesn't make any difference it may be avast that is being blocked:
What is your firewall ?
Does it allow avastSvc.exe internet access ?
- If it does delete the entry for it and do a manual update and reconnect to the internet, this should force the firewall to ask permission again. avast.setup