Make sure your system, whatever it is, is totally up to date, that includes any parts of it that you don't use (such as IE if you use another browser, for example).
Go to Control Panel > Programs and uninstall all McAfee products Then run the MCPR cleanup tool listed under Useful Links at the top of this page, reboot and reinstall your product from the online account.
If that fails to cure the issue then contact Technical Support, it's free by phone or online chat and available through Useful Links above.
If you use Registry Cleaners, stop. Those can cause this issue.