I have been using my HP 3570c flatbed scanner and my Nikon CoolScan V ED film and slide scanner with both Jaunty and Karmic. The applications I use are XSane and Vuescan (only the Nikon). Suddenly today, these two applications do not find my Nikon. I ran the following in a terminal:

Code:
~$ lsusb
Bus 002 Device 007: ID 04b0:4001 Nikon Corp. LS 50 ED/Coolscan V ED
Bus 002 Device 005: ID 0bc2:3001 Seagate RSS LLC 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 003: ID 03f0:1212 Hewlett-Packard 
Bus 003 Device 002: ID 045e:0040 Microsoft Corp. Wheel Mouse Optical
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 004: ID 0930:6545 Toshiba Corp. Kingston DataTraveler 2.0 Stick (4GB) / PNY Attache 4GB Stick
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 004: ID 413c:2006 Dell Computer Corp. 
Bus 006 Device 003: ID 03f0:2005 Hewlett-Packard ScanJet 3570c
Bus 006 Device 002: ID 413c:1004 Dell Computer Corp. 
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub


~$ sudo sane-find-scanner

  # sane-find-scanner will now attempt to detect your scanner. If the
  # result is different from what you expected, first make sure your
  # scanner is powered up and properly connected to your computer.

  # No SCSI scanners found. If you expected something different, make sure that
  # you have loaded a kernel SCSI driver for your SCSI adapter.

found USB scanner (vendor=0x04b0 [Nikon], product=0x4001 [LS-50 ED]) at libusb:002:007
found USB scanner (vendor=0x03f0, product=0x2005) at libusb:006:003
  # Your USB scanner was (probably) detected. It may or may not be supported by
  # SANE. Try scanimage -L and read the backend's manpage.

  # Not checking for parallel port scanners.

  # Most Scanners connected to the parallel port or other proprietary ports
  # can't be detected by this program.


~$ sudo scanimage -L
device `hp3500:libusb:006:003' is a Hewlett-Packard ScanJet 3500 scanner
device `coolscan2:usb:libusb:002:007' is a Nikon    LS-50 ED         film scanner
device `hp_rts88xx:libusb:006:003' is a Hewlett-Packard ScanJet 3530C flatbed scanner
device `hp_rts88xx:libusb:006:003' is a Hewlett-Packard ScanJet 3570C flatbed scanner

~$ scanimage -L
device `hp3500:libusb:006:003' is a Hewlett-Packard ScanJet 3500 scanner
device `hp_rts88xx:libusb:006:003' is a Hewlett-Packard ScanJet 3530C flatbed scanner
device `hp_rts88xx:libusb:006:003' is a Hewlett-Packard ScanJet 3570C flatbed scanner

So, I have a few questions.

(1) Is this about permissions?
(2) If so, is the file I need to set permissions on /dev/bus/usb/002/007?
(3) If things are correct so far, to what do I need to set the permissions?
(4) Why would my permissions have changed?