I have the same issue. Why no replies? We can't be the only 2 people with this issue.
I am using the latest version of Avast Free, 2014.9.0.2008 , which oddly you can't highlight and copy the text of the version info from the about screen.
Using Windows 8.1 x64 with the latest updates as well.
When I use 7zip to unzip a file. I am getting a false positive. The pop up window from Avast has an option of "Add the file to the scan exclusion list", but when I click it nothing happens. It also has an option to submit the false positive and that option works when I click on it. If this has been an issue for at least 6 months, why is it not fixed. Or at least, why are there no replies to this thread?