Log in as an administrator.
Open Terminal (in /Applications/Utilities).
Type the following commands, each on a single line and followed by Return (enter an admin password when prompted):
sudo dscl . create /Groups/username GroupMembership username
sudo dscl . change /Groups/username RecordName username _username
Replace the italicized “username” with your account username (which is also the name of the user’s Home folder, in the Users folder). Remember to include the underscore “_” before your user name in the second command.
If you have more than one account on the computer affected by this issue, you should run these two commands again for each account, substituting with the appropriate user name each time.
This document will be updated as more information becomes available.