There was an error encrypting or decrypting credentials. Either a credential update is currently being performed, or you must update the farm account credentials on this server before you can perform this task.

Solution:

   Steps:.

1.  Open SharePoint 3.0 Central Administration, click Operations, and then click Timer job definitions under Global Configuration.

2. Verify that the Administration Application Pool Credential Deployment job definition is no longer displayed in the list. 

3. Delete the Administration Application Pool Credential Deployment job definition, if it is still available.