If you have OIT's previous antivirus software, ClamXav, installed on your system, you need to uninstall it.
If you no longer have your download file, please visit http://www.clamxav.com/download.php and download the associated file before starting the process below.
Locate the ClamXav installer you downloaded
Find ClamXav in your Applications and drag it to the trash can. Do the same for the uninstaller.