Moved to VirusScan as a more appropriate spot for support.
System is up to date. Ran the Virtual Technician...it apparently fixed some problems with registry, but I still have other problems--it says missing files, etc. It appeared to fix most issues, however. But when I went to click Turn On Real-scanning again, it still acts like it works...and a few seconds later goes back to red.
Have you run any kind of registry cleaners lately? These are notorious for causing this kind of thing. If so see if there's a reverse setting. If not, check for malware using perhaps Stinger and then Malwarebytes Free, see the last link in my signature below. Also make sure that Internet Explorer, even if you don't use it, is up to date and at default settings. (The McAfee interface uses it).
Then if no improvement try uninstalling everything via Control Panel > Programs
Then run the MCPR cleanup tool and reboot.
Then reinstall your software from your online account.
If that fails to cure the situation, contact Technical Support direct.
It's free by phone or online chat and linked under Useful Links at the top of this page.