This has been an “on and off” issue with v8.0.xxx Have you tried the latest v8.0.1497?
http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe http://files.avast.com/iavs5x/avast_pro_antivirus_setup.exe http://files.avast.com/iavs5x/avast_internet_security_setup.exe http://files.avast.com/iavs5x/avast_premier_antivirus_setup.exe