Exclude virusscanners from touching a live db, good anti virus programs will have options to exclude specific programs.
It's OK to do virus checks on backups.
Specifically ....do not virus scan the hosted files while they are hosted.
Do not use anything other than FMS to backup the hosted files while they are hosted.
Both of these scenarios can cause corruption and its a costly fix.
In a nutshell don't let ANYTHING touch the hosted files while they are hosted other than FileMaker Server.
Are you talking about AV on the clients or on the server?
Client.. host is naked