using xsane as non-root user

[Amadeus W.M.]

Precisely what is the reason xsane can't be used as non-root users? 

I have a usb-connected Brother all-in-one. In F8 I was able to use it as 
myself. No longer so in F9, with an I/O error which I suspect was due to 
the 660 permissions on the appropriate /dev/usb device. I can use it as 
root just fine.

In what obscure udev/hal file do I have to change 660 to 666? I found


ACTION=="add", KERNEL=="sg[0-9]*", BUS=="scsi", ATTRS{type}=="3|6", SYMLINK
+="scanner scanner-%k", MODE="0660"

in /etc/udev/rules.d/40-redhat.rules

Is this the right place? Should I?

In fact, I just changed the permissions manually to /dev/usbdev* and I'm 
getting the same error:

Failed to open device `brother2:bus4;dev2':
Error during device I/O.

Any help?