A few memebers of my forum say they are getting a virus warning
 

I downloaded a backup of my entire forum, and unzipped it and checked it with AVG and with Malwarebytes. I didn't get any indications that I had any viruses or trojans on my forum.

It is only 3-4 members who say that. Is there a good way to check to see if there is any viruses hidden in my forum?

I'm wanting to upgrade to a newer version of vBulletin, and I don't want to do that until I know for sure if my database and everything else is clean.

My forum is www.dirtydozensbunker.com