1. If a McAfee "anti-virus" product is installed, remove it by following the instructions on whichever of the pages linked below is applicable:
How to install or uninstall McAfee Internet Security for Mac
How to manually remove VirusScan for Mac 8.6.x using a removal script
How to uninstall and reinstall McAfee Agent 4.x on Macintosh computers
Note that if you have already tried to uninstall the software, you may have to reinstall it in order to finish the job. If you have a different version of the product, the procedure may be different.
Back up all data before making any changes.
2. If you synchronize Contacts with one or more network services such as iCloud or Google, disable all the contact accounts in the iCloud and/or Internet Accounts pane of System Preferences. When prompted to confirm, choose to delete the contacts from the Mac. They'll still be on the servers and on your other devices.
Log out or restart the computer.
If the problem is resolved, re-enable the accounts one at a time, wait for the network contacts to reappear, and test after each step.
Credit for this observation to ASC member tomconrad.