I am having similar problems. I am W2K, Zone Alarm(all avast allowed), TDS-3, Spywareblaster,SpyBot S&D Resident IE protection, and as mentioned above-Google as home page.
I havenot experienced any problems until today, when I tried to log in to my router to look at the log(something I do every few days as a habit). That's when I saw the Avast error page, something else I have never seen before! The thing is that once I get that error page, the only way I can get any type of connection back at all is to reboot. This includes disabling the web scanner, and even as an investigation, disabling Avast entirely. As much as I was beginning to prefer Avast over my previous(removed) AV, I am unhappy with this trade-off.
Any suggestions?