Problem with devices(/dev/sg*) using two scanners

I've an agfa snapscan 310 scsi connected to de back of an Epson Filmscan 200.
        The Epson Filmscan 200 is connected on a scsi card.
        Both scanners are recognized on win xp and on linux mandrake 9.2 in vuescan 8.4.31...

        In Ubuntu feisty Fawn 2.6.20-16-generic (under Gnome), it appears that the devices are changing in "/dev/sg*"
        After a reboot, only the Agfa is recognized but if I change an other "sg*" other than the "sg*" of the scanner Agfa or of the cdrom, and I put it in scanner group, both scanners are recognized for this session if I restart vuescan 8.4.31...
        The problem is that what is modified in "/dev/sg*" in a ubuntu session for the Epson is changed when I reboot the system and then, the Epson will not be recognized.

        For example, after reboot the followings commands give this:
        ----------------------------------------------------
        h2007@ubuntu:~$ ls /dev/sg* -l
        crw-rw---- 1 root root 21, 0 2007-09-26 17:56 /dev/sg0
        crw-rw---- 1 root root 21, 1 2007-09-26 17:56 /dev/sg1
        crw-rw---- 1 root cdrom 21, 2 2007-09-26 17:56 /dev/sg2
        crw-rw---- 1 root cdrom 21, 3 2007-09-26 17:56 /dev/sg3
        crw-rw---- 1 root scanner 21, 4 2007-09-26 15:57 /dev/sg4
        crw-rw---- 1 root root 21, 5 2007-09-26 15:57 /dev/sg5
        h2007@ubuntu:~$ cat /proc/scsi/scsi
        Attached devices:
        Host: scsi0 Channel: 00 Id: 00 Lun: 00
          Vendor: ATA Model: WDC WD600AB-60CB Rev: 04.0
          Type: Direct-Access ANSI SCSI revision: 05
        Host: scsi0 Channel: 00 Id: 01 Lun: 00
          Vendor: ATA Model: SAMSUNG HD400LD Rev: WQ10
          Type: Direct-Access ANSI SCSI revision: 05
        Host: scsi1 Channel: 00 Id: 00 Lun: 00
          Vendor: SAMSUNG Model: DVD-ROM SD-616T Rev: F307
          Type: CD-ROM ANSI SCSI revision: 05
        Host: scsi1 Channel: 00 Id: 01 Lun: 00
          Vendor: SAMSUNG Model: CD-R/RW SW-240B Rev: R407
          Type: CD-ROM ANSI SCSI revision: 05
        Host: scsi2 Channel: 00 Id: 03 Lun: 00
          Vendor: AGFA Model: SNAPSCAN 310 Rev: 1.20
          Type: Scanner ANSI SCSI revision: 02
        Host: scsi2 Channel: 00 Id: 06 Lun: 00
          Vendor: EPSON Model: FilmScan 200 Rev: 1.01
          Type: Processor ANSI SCSI revision: 01
        h2007@ubuntu:~$
        ------------------------------------------------------
        Only the Agfa is recognized by this way in sg4.
        I close vuescan and I do:
        h2007@ubuntu:~$ sudo gnome-commander
        I go to /dev/sg5 ==>Properties ==> Autorisations ==> and I change the group from root to scanner.
        Then restart vuescan and both scanners are recognized!!!

        I shutdown the computer, power on for both scanners before; power on for the computer, starting ubuntu and:
        ------------------------------------------------------
        h2007@ubuntu:~$ ls /dev/sg* -l
        crw-rw---- 1 root scanner 21, 0 2007-09-26 18:24 /dev/sg0
        crw-rw---- 1 root root 21, 1 2007-09-26 18:24 /dev/sg1
        crw-rw---- 1 root root 21, 2 2007-09-26 18:24 /dev/sg2
        crw-rw---- 1 root root 21, 3 2007-09-26 18:24 /dev/sg3
        crw-rw---- 1 root cdrom 21, 4 2007-09-26 18:24 /dev/sg4
        crw-rw---- 1 root cdrom 21, 5 2007-09-26 18:24 /dev/sg5
        h2007@ubuntu:~$ cat /proc/scsi/scsi
        Attached devices:
        Host: scsi0 Channel: 00 Id: 03 Lun: 00
          Vendor: AGFA Model: SNAPSCAN 310 Rev: 1.20
          Type: Scanner ANSI SCSI revision: 02
        Host: scsi0 Channel: 00 Id: 06 Lun: 00
          Vendor: EPSON Model: FilmScan 200 Rev: 1.01
          Type: Processor ANSI SCSI revision: 01
        Host: scsi1 Channel: 00 Id: 00 Lun: 00
          Vendor: ATA Model: WDC WD600AB-60CB Rev: 04.0
          Type: Direct-Access ANSI SCSI revision: 05
        Host: scsi1 Channel: 00 Id: 01 Lun: 00
          Vendor: ATA Model: SAMSUNG HD400LD Rev: WQ10
          Type: Direct-Access ANSI SCSI revision: 05
        Host: scsi2 Channel: 00 Id: 00 Lun: 00
          Vendor: SAMSUNG Model: DVD-ROM SD-616T Rev: F307
          Type: CD-ROM ANSI SCSI revision: 05
        Host: scsi2 Channel: 00 Id: 01 Lun: 00
          Vendor: SAMSUNG Model: CD-R/RW SW-240B Rev: R407
          Type: CD-ROM ANSI SCSI revision: 05
        h2007@ubuntu:~$
        --------------------------------------------------------
        Only one scanner (Agfa) and not on the same place as before...
        I go to /dev/sg1 ==>Properties ==> Autorisations ==> and I change the group from root to scanner.
        Then restart vuescan and both scanners are recognized!!!
        -----------------------------------------------------------

        Have you an idea to fix it?
        Thanks for reply.
        Hubert Maes.