Are you using any kind of password to protect the console. Try unlocking it!
Since the computer had/has malware on it, the malware has probably corrupted the installation.. It's a common result of such infections..
First, you'll need to confirm that you have no malware on the machine.. I'll recommend updating Malwarebytes and running it repeatedly till nothing is detected.. Once that's done, try a second free tool from the link below:
SUPERAntispyware Removal Tool
Next, manually update VirusScan by downloading the Superdat file from the link below.. Download the file to your desktop, then run it to install the most current 5400 scan engine and the current definition files:
After that, if things aren't fixed, it's time to do a full uninstall of VirusScan, then reinstall it, making sure you have the most current Patch #8 installed for VS 8.5i.. For the full manual uninstall instructions, see the link below:
Manual Uninstall Of Virus Scan Enterprise 8.5i
Hope this helps.
Now i think McAfee VirusScan Enterprise is 8.7i. So you should update to latest version.