Hi,after some more investigation, the problem was that my udev setup was broken ; adding back the right udev rule made the problems go away.
I'm still baffled why scanning from remote worked though : that is the reason why I had ruled out permissions issues...
Thanks, Snark on #gnome-hackers -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org