Malka, if you have a DSL connection to Internet, please, make sure you add AlwaysConnectedWaitSeconds=60 after the line AssumeAlwaysConnected=1.
This way you will wait 60 seconds after a connection is detected to update avast. If you have a ‘stressed’ boot (many programs loading…) this could make it work.
More details click on ‘Settings’ in my signature 