Netbackup shows: Media is in use

Hello,

Suddenly, I see in the Netbackup console, when i start a backup task, the state is MEDIA IS IN USE and not running at all. I tried to cancel the job, restart the Storage library, restart the server, but remained the same state Media is in Use till sometime later after restart...

I would like to know from where, and what could help diagnosing this issue...

Thanks in advance!