Try a reboot into Safe Mode and then running it again. In Safe Mode you can't open the SecurityCenter, simply right-click the taskbar icon and select Scan or go into Windows Explorer and right-click the hard drive and select Scan.
Please confirm if McAfee is Upto date by posting the Version details here. Also Navigate to the "Quarantined and Trusted Items" and try deleting the detections from there.
To do this try the below steps
Open McAfee UI > Navigation > Quarantined and Trusted Items > Quarantined PUPs > Select the Detection and Click delete.
You may also try this in Safe Mode as well..!
It could be files that your computer needs to make your system run or antivirus doesn't have the right file to remove them. Your computer is safe when they are quarntined.