The problem was reported first by jfraga@dq.fct.unl.pt in
https://bugzilla.novell.com/show_bug.cgi?id=153128#c8

After configuring a USB scanner it must be unplugged from the USB
and re-plugged to trigger the udev -> HAL -> resmgr chain to allow
normal user access.

Details:
To make a new configured USB scanner accessible for normal users
the whole udev -> HAL -> resmgr machinery must be triggered
so that in the end resmgr allows access for normal users.
Normally during booting or when a scanner is new plugged into the USB
udev gets an event and then udev triggers hald which processes the
/etc/hal/fdi/policy/10osvendor/80-scanner.fdi
file so that hald triggers resmgr which allows normal user access
for the USB device node.
But for an already plugged in scanner this chain does not work.
It is not possible to trigger HAL to processes the 80-scanner.fdi file
on demand.
Furthermore even "echo 1 >/sys/complicated/path/uevent" does not work
to trigger udev for USN scanners (for other hardware it should work).
Therefore the only reliable way at the moment is a user information
in the YaST scanner configuration to re-plug the scanner.