Possibly tempdb out of space or a system table is inconsistent
DBCC CHECKDB makes extensive use of tempdb. It relies on a mechanism similar to snapshot isolation to make sure it always sees a transactionally consistent image of the database, independent what else might be going on.

The error you receive is most likely due to the fact that there is not enough room on the drive that tempdb is on. However, the error also states to check any prior errors. Were there any?