system
3
This sounds like this thread:
http://forum.avast.com/index.php?topic=78128
In Avast, go to Settings, Troubleshooting and enable "Load Avast services only after other...".
It never broke mine as well - but there have been quite some complaints about this, always same symptoms: boot PC - no browser web. Stop web shield, start browser, enable web shield: all is fine until next reboot. :o And in all cases the "Start Avast services only after other..." did the trick...