Assuming you have not a virus or malware I suggest uninstalling Mcafee and reinstalling it see the link in my sig. After uninstalling it and rebooting run
and reinstall from your account
After the reinstall if issue still therer try same of the scanners I mention in my signature link. With malwarebytes do not install the trial of the premium version as it can clash with Mcafee.
Another thought before you do the above is go to navigation/ general settings and alerts and access protection and disable access protection retry the update and then reenable access protection.
Also please install IE11 as McAfee relies on the latest available version of IE being installed and set to default settings. It doesn't have to be your default browser however. I also hope this is Windows 7 SP1.
Branched this to its own thread as the original solved thread was 3 years old and reasons for issues and solutions change over time.