First have you Internet Explorer and all windows updates installed up to date?
IE must be updated as McAfee uses it also have you another virus scanner installed such as Norton or paid versions of some malware scanners?
If you have remove them and for the Norton type scanners use their own removal tool to do it.
Remove McAfee or rather anything you have partly installed via the steps in the link in my signature below. Reboot and run
and reinstall from your account
If still an issue call tech support as per the link below for your country it is free.
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