HP Deskjet 3520 Scanner not detected

I just bought an HP Deskjet 3520 all-in-one for the sole purpose of replacing my old Canon, specifically because the Linux support seemed better for HP's in general and I checked beforehand that this model was fully supported. Scanning worked fine with the Canon, so this is little frustrating. In any case, I'll get on with the description of the problem.

I'm running Linux Mint 12 with the latest download of HPLIP 3.12.6.

Scanning from the HP Device Manager gives the error message :
"Failed to open device `hpaio:/usb/Deskjet_3520_series?serial=CN26H122G205SY': Operation not supported."

Here's the output of 'hp-check -t' : http://codepad.org/ljx9uc39

I added myself to the 'scanner' group, though this wasn't necessary before.
$ groups
olivas adm lp dialout cdrom plugdev scanner lpadmin admin sambashare

$ hp-probe
...
--------------------
| DEVICE DISCOVERY |
--------------------

  Device URI Model
  ------------------------------------------------- ----------------------
  hp:/usb/Deskjet_3520_series?serial=CN26H122G205SY HP Deskjet 3520 series

Found 1 printer(s) on the 'usb' bus.

Here's the relevant output from 'lsusb -v' (http://codepad.org/Wl6i134C) which tells me the write permissions are set correctly.
Many of the other lines say, for example :
  Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
  libusb couldn't open USB device /dev/bus/usb/007/001: Permission denied.
  libusb requires write access to USB device nodes.
  Couldn't open device, some information will be missing

$sane-find-scanner
found USB scanner (vendor=0x03f0 [HP], product=0xb011 [Deskjet 3520 series]) at libusb:001:003

$scanimage -L
No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).

Here's the output with the logging level ratcheted up : http://codepad.org/nu4qKN1S

Printing works just fine and I've tried to scan with both xsane and simple-scan and neither can detect the scanner.

I also checked the scan-type (in models.dat) is not 0. It's '7' but then again I really don't know what that means.

Any help would be greatly appreciated.
Thanks,
Alex.