Well firstly if you have Norton and avast on your system at the same time you are heading for possible conflict. Also if the above is correct avast should be able to detect the presence of Norton and is likely to disable elements to avoid conflict, this could possibly account for it not being scanned.
What is Norton saying it is ?
You should also confirm it is a good detection. 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/quarantine, you will need to move it out.If it is a good detection, you are not getting a virus warning that you believe is a new, undetected virus then if you can zip and password protect ('virus', will do) the suspect file and send it to virus @ avast.com (no spaces), or send from the chest (after adding it to the User Files section of the chest).
Give a brief outline of the problem (possibly a link to this thread), the fact that you believe it to be a either a new or undetected virus 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.
