For the last week, many of my normal visited websites were being blocked/ extremely slow loading/ or timing out. I could go to plenty of other websites such as cnn.com, amazon.com, google search, etc and move freely, stream video, etc. But, many other websites, yahoo.com, yahoo mail, facebook, mozilla homepage, gmail would not load. After quite a bit of troubleshooting with Comcast Xfinity advanced support, I turned off the Web Shield and suddenly Firefox and Chrome were back able to to go to all websites. Then under Avast WebRep, I found the reference to the Safari extension, went into Safari Preferences/ Extensions and turned off Enable Web Rep extension.
But, none of these problems were happening when I took my laptop to a different wifi - I didn't have to change anything about Avast. So, it appears something in Comcast Xfinity high speed internet is conflicting with the latest update of Avast for Mac ver 7.0
I am glad my internet is working, but I want the web shield back on....more trial and error.