be 2010 on an hp autoloader going offline during backup.
Ensure hardware is working fine by running hardware diagnostics
Try the t/s steps on this article
Refer http://www.symantec.com/docs/TECH70907 (if controller is a raid)
Please share some more details (upload the adamm.log from BE Install Path\Logs folder)
Best thing to do is to download Hp Library and Tape Tools (HP LTT) from the HP website.
Stop the BE services, and then run the diagnostic checks against the device. This will rule out an issue with the hardware itself. From previous experience, it was always pointing to a faulty drive in my case!
Also make sure you are running the latest Symantec drivers for the device, and if the server is Windows Server 2003, stop and disable the Removeable Storage service.
If you find this is a solution, please mark it as such.