Hola, si haz llegado acá es por este error:
warning: Missing REQUIRED dependency: cups-image (CUPS image - CUPS image development files)
Te preguntas, ¿cómo solucionar este problema?
es muy simple, "apt-get install libcupsimage2-dev"

Debian SID
Linux Maximiliano 2.6.29-1-686 #1 SMP Fri Apr 17 14:35:16 UTC 2009 i686 GNU/Linux


HP Linux Imaging and Printing System (ver. 3.9.4)
HPLIP Installer ver. 5.0

Copyright (c) 2001-9 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Installer log saved in: hplip-install_Sun-26-Apr-2009_19:09:50.log

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note: Defaults for each question are maked with a '*'. Press to accept the default.


INSTALLATION MODE
-----------------
Automatic mode will install the full HPLIP solution with the most common options.
Custom mode allows you to choose installation options to fit specific requirements.

Please choose the installation mode (a=automatic*, c=custom, q=quit) :

Initializing. Please wait...


INTRODUCTION
------------
This installer will install HPLIP version 3.9.4 on your computer.
Please close any running package management systems now (YaST, Adept, Synaptic, Up2date, etc).


DISTRO/OS CONFIRMATION
----------------------
Distro appears to be Debian unstable.

Is "Debian unstable" your correct distro/OS and version (y=yes*, n=no, q=quit) ?


SELECT HPLIP OPTIONS
--------------------
Would you like to enable support for parallel (LPT:) connected printers? (y=yes, n=no*, q=quit) ?


ENTER ROOT/SUPERUSER PASSWORD
-----------------------------
Please enter the root/superuser password:
Password accepted


RUNNING PRE-INSTALL COMMANDS
----------------------------


INSTALL MISSING REQUIRED DEPENDENCIES
-------------------------------------
warning: There are 1 missing REQUIRED dependencies.
note: Installation of dependencies requires an active internet connection.
warning: Missing REQUIRED dependency: cups-image (CUPS image - CUPS image development files)
warning: This installer cannot install 'cups-image' for your distro/OS and/or version.
error: Installation cannot continue without this dependency. Please manually install this dependency and re-run this installer.