Backup exec will display "loading media" if there is no media in the drive, the media that is in has an overwrite protection period set on it e.g. 24 hours, and you are still in that protection period, or if the media is not in the backup media set that Backup Exec has been configured to use. I would cancel the job and check the media. You can add it to the media set if you choose "Media Set" on the admin screen and then try a backup again