Maybe a variant, polimorphism or whatever… I’m not a virus expert. Again, I’m not apologizing (I’m not from avast team ;D), just telling you that could be a problem of configuration, the user must know how the programm (and its parts) works, etc.
Well, it’s not so bad… Try any other antivirus company. It’s summer holidays now. But, sorry, I feel your pain and don’t want to give an answer for all your needs… It’s a pity what happened. What can we do now?