You most likely have a mismatch between the kerberos principal defined on the KDC and the keytab on you cluster nodes. Give this a try and it should fix you right up...
- Stop all services, including the Cloudera Management Service.
- Go to: Administration > Security > Kerberos Credentials
- Select all Principals
- Click "Regenerate Selected"
- Restart all services and hope for 'green lights' ;-)