I have a small sharepoint farm that I am trying to backup.  However, I get the following intermittent error the causes the job to fail:

SharePoint -- The job failed with the following error: The logon account that was provided does not have valid credentials. Ensure that the user name and password are correct, and then try again.

I have not changed the logon account.  If I try to check the credentials, quite often BackupExec will crash and will require a restart.  If the program does not freeze, the credential check succeeds.

How do I get this job running again?