Hi, I’m assuming you are referring to AOS> The issues with Avast Online Security(Browser Protection Option) have been widely reported with what you are describing (with myself as well).
You can disable Avast Online Security Plug in found in Brower Add ons.(as I think you may have done)
OR you can uninstall Browser Protection(AOS) by Control Panel/ Programs/Features and chose Avast then choose ‘Change’ and uncheck ‘Browser Protection’. 