sane-find-scanner finds it, scanimage -L does not

[Wybo Dekker]

I have an Epson Perfection V350 scanner and two machines with jaunty:
- an HP-Compaq, where the scanner works flawlessly, and
- a NEC, where sane-find-scanner finds it, but scanimage -L does not.

The relevant files on both machines are the same:
- /etc/sane.d/dll.conf (completely commented out)
- /etc/sane.d/epkowa.conf (with usb 0x04b8 0x012f, pointing directly to
   the scanner)
- /etc/sane.d/dll.d/hplib (completely commented out)
- /etc/sane.d/dll.d/libsane-extras (commented out, except for epkowa)
- /etc/udev/rules.d/45-libsane.rules (was absent on the NEC, copied it
   from the compaq)

sane-find-scanner says, on both machines:
found USB scanner (vendor=0x04b8 [EPSON], product=0x012f [EPSON 
Scanner]) at libusb:001:003

scanimage -L says on the Compaq:
device `epkowa:libusb:001:003' is a Epson Perfection V350 flatbed scanner

but on the NEC:
No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).

and in debug mode:

SANE_DEBUG_DLL=7 scanimage -L
[sanei_debug] Setting debug level of dll to 128.
[dll] sane_init: SANE dll backend version 1.0.12 from sane-backends 1.0.19
[dll] sane_init/read_dlld: processing /etc/sane.d/dll.d ...
[dll] sane_init/read_dlld: considering /etc/sane.d/dll.d/libsane-extras
[dll] sane_init/read_config: reading dll.d/libsane-extras
[dll] add_backend: adding backend `epkowa'
[dll] sane_init/read_dlld: considering /etc/sane.d/dll.d/hplip
[dll] sane_init/read_config: reading dll.d/hplip
[dll] sane_init/read_dlld: done.
[dll] sane_init/read_config: reading dll.conf
[dll] sane_get_devices
[dll] load: searching backend `epkowa' in `/usr/lib/sane'
[dll] load: trying to load `/usr/lib/sane/libsane-epkowa.so.1'
[dll] load: dlopen()ing `/usr/lib/sane/libsane-epkowa.so.1'
[dll] init: initializing backend `epkowa'
[dll] init: backend `epkowa' is version 1.0.208
[dll] sane_get_devices: found 0 devices

No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).
[dll] sane_exit: exiting
[dll] sane_exit: calling backend `epkowa's exit function
[dll] sane_exit: finished

I hope the list can give me a hint...
-- 
Wybo