Update problem

[demonperformer]

I am using Firefox browser.
A couple of days ago my system automatically updated the Avast Program to 2014.9.0.2016.
Ever since then, every time I fire up the browser, it automatically opens a second window with http://aos.avast.com/upgrade/2006 in it.
I can find no way of stopping it from doing this.
The only link I can see on the page takes me to chrome://wrc/content/options.html - but even if I change those settings and press 'save' it (a) does not save them, reverting the settings to the same as before, and (b) does not stop this new window from opening every time I fire up the browser.
This is really starting to irritate me, so please advise how I can get it to stop.
Thanks.

[Asyn]

You've to keep this cookie: aosbrowserpluginlocalstoragescope.com

[demonperformer]

I've added that address to my "exceptions" list, but it still fires up every time.  Do I need to do something else? Thanks.

[demonperformer]

Just found a previous thread (http://forum.avast.com/index.php?topic=148337.0) that recommends removing the offending bit of the program - giving it a try.
Thanks.