The issue is that one of your smart groups is broken.
The low-tech approach to figuring out which is to disable half of your smart groups, run the "Rebuild Smart Group Cache" scheduled job (Administer menu » System Settings » Scheduled Jobs) and check its job log to see if the problem group is in the disabled half or enabled half. Keep eliminating half the groups at a time until you've found the troublesome group.
Review its criteria (in Contacts menu » Manage Groups) and see if there's an obvious alternative (or if you even need the group anymore).
If you have more tech skills, you can download my smart group profiling script. This requires you have cv installed. Its original purpose is to find smart groups that are slow, but if you have a failure like the one you describe, it will fail on that group, and the last group listed is the one that failed.