Are you using Avast! 5?
The chest is accessible through the UI. Open Avast!, it is in the maintenance section.
Avast put a file that is part of my scanner program into the Virus Chest. It is a perfectly legitimate file.
You say this, but are you aware the are viruses that infect legitimate files on your PC? Could you post a screenshot of the detection?
What is this "scanner program" you speak of? If it runs on-access, extracting it from chest, Avast! will likely just throw it back in again. Thus you would also need to set an exclusion for it.
ps/your email address is showing, you may wish to hide it (Profile>>AccountRelated Settings>>Check "Hide Email") to avoid getting spam harvested.