SDT9000 - ML350 - NTBackup stops after a few GB

[Ayman Altounji]

I have a Compaq ML350 Server with a SDT9000 internal tape drive.
When I use NTBackup to backup some data the backup stops after a few GigaBytes en reports "Tape device reported an error on a request to write data to tape." in the backup log.
I applied SP6a for Windows NT4.0.
Installed the latest compaq driver for this tape drive.
Updated the firmware of the tape drive.
I even had the tape drive replaced by a spare one by Compaq.
And of course I tried using new tape media.

Any ideas ?

Wim Raets