Is your machine managed by ePolicy Orchestrator (ePO) ?
If this is the case, the option may well have been disabled from ePO and can only be administered through ePO.
I don't know what 'ePO' is, but you're probably right.
Thanks for the answer.
ePolicy Orchestrator (ePO) is management software that allows administration of workstations from a central location.
I suffer from the exact same thing, every month or so. Don't know how this happens.
I do know the solution for enabling the scanner again:
and download the superdat file.
Install the file and reboot the computer.
You find this problem all over internet. I don't understand why McAfee can't solve this problem. (I run the latest patch)