On a server I wouldn't expect Norton... that is for desktop protection and uses way too many resources for a web server. ClamWin/ClamAV are suggested for a server.
You should never install anti virus before your server and services, this can cause many issues installing files and programs required and if it is, you must disable it until the install is completed.
On another note, you should add those programs to your A/V's whitelist (or ignore list).
