Arcserve 9.01 on NW6.0spk5

Bought a new LTO-3 external drive about a month ago. it came with its
own scsi card, which I installed in the server (dell PE4600). Started
it back up, arcserve recognized the drive, and it was working fine
until a few days ago. We noticed that the backups started going very
slow...not finishing overnight. so we rebooted the server, and now
arcserve doesn't see the new drive at all.

I'm at a bit of a loss, because nothing has changed on the
configuration changes, or anything to arcserve, either.

I ran the dell diagnostics on the server, and it can see, read and
write to the drive without issue. Scsi channel shows up during the
server's post, it recognizes the drive as it should, ham drivers load
in netware...but arcserve just doesn't see it. It only recognizes the
server's original tapedrive, which is an internal model that is
physically broken. (spits out tapes...which is why we bought the
external replacement).

so its acting like a hardware failure...(sudden software
changes), but diagnostics say it it must be software. or is