Backup job failed could not log on.

If I run the job manually it works just fine. If I test the credentials it works just fine. Having to reinstall the agent and the job all the time is starting to get very annoying when it fails. Has any one ever had such repetitive issues like this?

Job ended: Monday, December 01, 2014 at 12:04:01 AM
Completed status: Failed
Final error: 0xe0009b61 - Backup Exec could not log on to the server with the logon account specified for it. The logon account does not have valid credentials. Ensure that the user name and password are correct in the logon account.
Final error category: Security Errors