@boot_wb

it looks like that MorphosTeam fixed USB :)

ok so:
download: http://brain.umcs.lublin.pl/~rzookol/download/mustek_usb/mustek_usb.device
download: http://brain.umcs.lublin.pl/~rzookol/download/mustek_usb.conf

copy mustek_usb.conf to s:

run SCANdal,
choose Scanner driver: mustek_usb.device with full path
Device leave blank
Unit: 0

scanner has to be unbinded in poseidon prefs

It should work (other scanners handled by mustek_usb backend too) :)