Does anyone know why udev (or sane?) sometimes seems to ignore the rules in the /lib/udev/rules.d directory?

A good example of what I mean is dealing with xsane & only being able to scan (or even detect a scanner) as root. People often have to make custom rules in /etc/udev/rules.d to get their scanner working. I've had to do the same in the past too. Even though both scanner devices I own were ALREADY in the /lib/udev/rules.d/53-sane.rules file.

In the end I just copied and pasted everything from the 53-sane.rules file to a custom file /etc/udev/rules.d/96-scanner.rules

Now xsane detects the three different scanners my laptop has access to with no problem (a Mustek 1200, Canoscan n1240u & another which is not mine). But shouldn't 53-sane.rules have allowed that anyway? All three scanners were given rules that already existed in 53-sane.rules, so why was a custom file needed in a different directory?

Is there something wrong with my permissions or arch-linux installation that makes the rules in /lib/udev/rules.d get ignored?

Well, yes and no would be my answer.

It seems that udev rules are being moved from /etc/udev/rules.d/ to /lib/udev/rules.d/ but this process is "in transition", and not yet completely implemented.

On my current distro (kubuntu 8.04) rules in /lib/udev/rules.d/ are ignored, but work when copied to /etc/udev/rules.d/

Thanks tredegar. That's good to know