Just read through this and having a problem w/ Avast refusing to allow a certain site at my local County, only if I use my non-secured (I'm in Noman's land) wireless modem. Have asked for opinions on another thread. Hardwired other provider allows me to go to this page fine with this laptop. I have Chrome and Windows 7 Professional, and Avast free.
This morning called the County - their IT fellow had no issues. I also tried using IE on my computer (which I almost never use anymore since it has issues) and could not get to the site.
Tried my old internet provider that doesn't use wireless, and no problem. As soon as I go back to using my wireless modem, voila, Avast's pop-up about securing my home network pops up, and I can't get to that County site. Blank page consistently.
Just added this in as perhaps the OP and I may be having some similar problem? Avast 800 tech said simply uninstall and reinstall. Why would that change anything?