Moved to Consumer > General as a better spot for it.
Make sure 8.1 is totally up to date, including App Updates (accessed through Store > Settings)
Make sure you have no other security software active.
Run the Virtual Technician to see if it finds and fixes problems: http://mvt.mcafee.com/
If that doesn't help try uninstalling via Control Panel > Programs and Features, then running the MCPR cleanup tool, reboot and reinstall from your online account.
If all else fails, Technical Support is free of charge and linked below.
Toronto ▪ Canada
Volunteer Moderator - Consumer Products
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