ntbackup stopped working on my DAT drive

[Larvoire]

Hi,

I have a PC under Windows XP, with an "HP C5683A SCSI Sequential Device" (a SureStore DAT 40)

All my nightly backups worked fine until june 6th.
Since then, none has worked.
The symptom is that the dialog "Backup Utility Looking for backup devices..
" stays on forever.
There's no OK, Cancel or Close button.
I have to kill the ntbackup.exe process to get rid of it.

I don't remember doing anything special that day. (Except leaving for one week of vacations :-)
I've rebooted the machine several times since then.
The device manager sees the DAT drive, and says it works OK.
I've tried 3rd party tools (MT.exe, found on the web): This works fine. Commands applied to the tape drive work.

I suspect a problem with the Removable Storage Manager.
The command:
rsm view /TDRIVE
fails with the message:
Unable to open session with the RSM server.

When I try to manually start the Removable Storage service (Is this the same as the "RSM server"?), I get an error:
"The Removable Storage service on Local Computer started then stopped.
Some services stop automatically if they have no work to do, for example, the Performance Logs and Alerts service."

Any idea that can help is welcome!

Jean-Françoi