From what you say it could be a false detection and needs to be confirmed.
You could also check the offending/suspect file at:
VirusTotal - Multi engine on-line virus scanner Or
Jotti - Multi engine on-line virus scanner if any other scanners here detect them it is less likely to be a false positive.
You can't do this with the file in the chest, you will need to move it out.If it is indeed a false positive, add it to the exclusions lists (
Standard Shield, Customize, Advanced and Program Settings, Exclusions) and periodically check it (scan it in the chest), there should still be a copy in the chest even though you restored it to the original location. When it is no longer detected then you can also remove it from the Standard Shield and Program Settings, exclusions.
Send the sample to
virus@avast.com zipped and password protected with password in email body and false positive in the subject.
Also see
(Mini Sticky) False Positives, how to report and what to do to exclude them until the problem is corrected.
