I have the same problem. Got several hits yesterday. In fact, Win32:Evo-gen [Susp] is the reason that any files at all are in my Virus Chest--some moved there yesterday, some moved there as far back as April 2013. When I extract any of them and re-scan them with Avast, they are reported as clean.
Also annoying: is the link on the virus warning popup the only way to report a false positive in Avast? I don't know if a file has a real virus or is false positive until I can examine it, compare it with an original, a backup, or a copy on another computer. That takes a time--by then the popup is gone.