This is an Epson Perfection V330 on Arch.

I had this scanner working as user with xsane for several months. Yesterday it would only work as root. This is a permissions problem but I do't know how to fix it.

I am a member of the scanner group.

I get the following with sane-find-scanner as user:

found USB scanner (vendor=0x04b8 [EPSON], product=0x0142 [EPSON Perfection V33/V330]) at libusb:004:003
could not open USB device 0x1d6b/0x0002 at 004:001: Access denied (insufficient permissions)
could not open USB device 0x1d6b/0x0001 at 003:001: Access denied (insufficient permissions)
could not open USB device 0x413c/0x3200 at 002:002: Access denied (insufficient permissions)
could not open USB device 0x1d6b/0x0001 at 002:001: Access denied (insufficient permissions)
could not open USB device 0x1d6b/0x0001 at 001:001: Access denied (insufficient permissions)

Scanimage -L says:

device `epkowa:interpreter:004:003' is a Epson Perfection V330 Photo flatbed scanner

The relevant entry in /lib/udev/rules.d/49-sane.rules is

# EPSON Perfection V330 Photo
ATTRS{idVendor}=="04b8", ATTRS{idProduct}=="0142", MODE="0664", GROUP="scanner", ENV{libsane_matched}="yes"

I tried using the lts kernel and also reverted to the previous version of xsane, but that didn't help.

I tried manually changing the owner/group of /dev/bus/usb/00*/00* but no effect.

I found plenty of posts about this on Google but nothing that fixed my problem.

Funnily enough, Vuescan does run the scanner as user.

Any ideas, anyone?

I finally found the "simple" solution myself after a day spent googling. I just deleted ~/.sane and allowed it to remake itself, after which user access was restored. I'm surprised no one else has reported this.