I’ve been using Avast for a long time (think since 4.0), and always had a setup with a squid proxy in my LAN, using an autoconfiguration script. Since updating to 2014, the web shield is blocking everything. It has been working with 8.x, but now I have to disable the proxy or the web shield.
I just installed Avast 2014 and encountered the same issue. I used to set it to localhost:12080.
(after version 6 I think it broke with ftp so I only use it for http traffic)