Here let us know if you are using a Standlone Tape drive and have selected the option of Eject Media in the Backup job properties. If answer to both these queries is YES then you need to check if there are any active alerts asking to Remove the Media.
The functioning is that the job will still show running even after all the data is backed up till the tape is manually removed from the tape drive or the Alert is reponded.
To avoid this you need to configure Automatic Reponse for the Remove Media alert category so that the job will show as completed before the tape is removed completely from the tape drive.
To set Automatic Response go to Active Alerts and select Configure Alert Category (on the left side pane) and then select Media Remove Alert. Then set the Automatic Reponse to 2 minutes. Then click OK to save the changes.
Here is the link to download and install the latest tape device drivers
http://support.veritas.com/docs/348315
Note: The link may take some time to open as Symantec is migrating the Knowledge base to new system
If this answers your query, please mark this as the solution.