Drove me nuts, too! Most of us clear out our cookies. And that's what causes it. I use CCleaner (free edition) and was able to eliminate it. In CCleaner go to Options, click on Cookies, then move
aosbrowserpluginlocalstoragescope.com
to Cookies to Keep. And it worked and saved my sanity! Was seriously thinking of dumping Avast for another security software before I solved this.