Not sure if this will help you or not but I recently also received this error. In our case it was an issue with how we had the "append to media" option set in our jobs. If the job is set to "append to media, terminate if no appendable media exists" and you are using a new tape or one that is full, then the job will terminate and it gave us the same error message that you are getting. We found in the docs where it says that to qualify as appendable media, a tape has to have at least one backup on it. Once we changed the option to "append, overwrite if no appendable available" our jobs have been working.