You could also check the offending/suspect file at:
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 you are getting a virus warning that you believe is a false positive, then if you can zip and password protect ('virus', will do) the suspect file and send it to virus @ avast.com (no spaces).
Give a brief outline of the problem, the fact that you believe it to be a false positive and include the password in the body of the email. Some info on the avast version and VPS number (see about avast {right click avast icon}) will also help.
If it is indeed a false positive, add it to the exclusions lists and check scan it periodically using the ashQuick scan (right click scan), when it is no longer detected then remove it from the exclusions.
