When backing up any licensed remote resources they may randomly fail for different jobs each time, and at different stages in the job if it is backing up multiple resources.
0xe000fe3c - Before you can back up this resource, you must purchase and install a license key for the appropriate Backup Exec agent
This issue is Fixed in Backup Exec 2010 R3 Release.
If you do "Retry Job Now" of the failed job or do "Run Now" for the scheduled job, the job will run successfully. You can also set up a rule in Tools | Error-handling rules to let the job run again if it fails with the described error. Also, if possible try to change the scheduling so less jobs are starting at the exact same time.