TL891 on a DL380 : connection problems

[BR757812]

Hello all !
Please be patient with me if I come over as a nitwit...

I'm having a problem getting a TL891 to work on a Proliant DL380-G3.
I'm using it in combination with the "157299-B21Dual channel Ultra SCSI adapter, differential (tape library connectivity)"-card, and a working cable.

If I connect the library to the SCSI-card, it is not seem by the system (Win2000 with ArcServe 2000), and i get an 'error 9 - The device, \Device\Scsi\cpq32fs21, did not respond within the timeout period. ' in the systemlog.

There is nothing wrong with either the library, tape drive or the cabling, since when I connect it to the internal SCSI Array Controller, it is recognised, and it works with the Compaq Tape Library Utility.
Yet when the library is connected to this array controller, ArcServe cannot use it : it tells me that the drive is on a 'shared interface' and that the primary server can't be reached ???

Any explanation ?
Thanks !