[CentOS] Missing UIDs

From time to time I'm seeing this message:

I couldn't find the numerical IDs of these users: abrt nslcd pulse rtkit saslauth tcpdump usbmuxd

In most cases this is caused by inconsistencies in the user or group database, e.g. between the files /etc/passwd, /etc/group and their respective shadow files /etc/shadow and /etc/gshadow. I will try to ignore these entries and continue for now, but please fix these inconsistencies as soon as possible.it </quote>

My first thought was to use system-config-user and create users with IDs matching their group IDs. However, doing it that way requires passwords to be set. How should I correct this?

Anne