Hi Jay,
Usually when these errors crop up on a regular basis like this its easiest to recreate that backup job. Chances are somewhere in the catalog is the problem. Does the job log not give any further indication to a problem with exception reports or failures?
I would first try recreating the backup job and running it again. Not the answer you want to hear Im sure but believe me when I say its going to be more time effective then trying to troubleshoot the problem.