Backup Exec 2012 R2 - Copy to tape terminates with Hardware error.

I have a HP MLS4048 Tape Library connected with SCSI to a server HP Proliant 380 G6, running Windows Standard Server 2008 R2.
With Microsofts drivers for Tape Drive installed, the backup goes smooth, but very slow, only 120 MB/min.

With Symantecs drivers installed, the job rate is about 2000 MB/min (!), BUT the job terminats after a while with Hardware Error.
This happens every time, either in the beginning of the backup job or after a while.

Anyone out there which have solution?

Thanks

Michael H.