I have been having the same issues. As an experiment, I took a small .jpg and scanned it with Avast, found to be clean. Then I used PGP to create a self-decrypting archive. I immediately had Avast report it had found win32:trojan-gen {VC}. Sounds like an Avast issue. I hope they fix it soon because I also discovered that no matter what Avast disposition you choose, it fubars the file. I don’t want Avast stomping on any critical files.