This problem disappeared some time ago when I started to use "Let printer determine colors" acroread advanced option. But, sadly, from some days (I am unable to know what update broke this) it fails even with that option. The same occurs when I manually try to print it using "lpr test.pdf", while other tools not using "lpr" work ok

What info do you need for trying to find the problem here?
app-text/ghostscript-gpl-8.71-r4 (the same with -r2, -r3, 8.70...)
net-print/cups-1.3.11-r2
net-print/hplip-3.10.2-r4 (the same with 3.9.12-r1)

My emerge --info:
Portage 2.1.8.3 (default/linux/amd64/10.0/desktop/gnome, gcc-4.3.4, glibc-2.10.1-r1, 2.6.32-gentoo-r7 x86_64)
=================================================================
System uname: Linux-2.6.32-gentoo-r7-x86_64-AMD_Athlon-tm-_64_Processor_3200+-with-gentoo-1.12.13
Timestamp of tree: Sun, 02 May 2010 15:00:01 +0000
ccache version 2.4 [enabled]
app-shells/bash:     4.0_p37
dev-java/java-config: 2.1.10
dev-lang/python:     2.6.4-r1
dev-util/ccache:     2.4-r7
dev-util/cmake:      2.6.4-r3
sys-apps/baselayout: 1.12.13
sys-apps/sandbox:    1.6-r2
sys-devel/autoconf:  2.13, 2.63-r1
sys-devel/automake:  1.9.6-r3, 1.10.3, 1.11.1
sys-devel/binutils:  2.18-r3
sys-devel/gcc:       4.3.4
sys-devel/gcc-config: 1.4.1
sys-devel/libtool:   2.2.6b
virtual/os-headers:  2.6.30-r1
ACCEPT_KEYWORDS="amd64"
ACCEPT_LICENSE="*"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=native -O2 -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/share/X11/xkb /usr/share/config /var/lib/hsqldb"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/env.d /etc/env.d/java/ /etc/fonts/fonts.conf /etc/gconf /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c"
CXXFLAGS="-march=native -O2 -pipe"
DISTDIR="/usr/distfiles"
FEATURES="assume-digests autoaddcvs ccache cvs distlocks fixpackages multilib-strict news parallel-fetch protect-owned sandbox sfperms sign split-log strict test unmerge-logs unmerge-orphans userfetch"
GENTOO_MIRRORS="ftp://ftp.free.fr/mirrors/ftp.gentoo.org"
LANG="es_ES.UTF-8"
LDFLAGS="-Wl,-O1"
LINGUAS="es es_ES en_US"
MAKEOPTS="-j2"
PKGDIR="/usr/local/portage/packages"
PORTAGE_CONFIGROOT="/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY="/usr/portage/local/layman/sunrise /usr/portage/local/layman/suka /usr/local/portage"
SYNC="rsync://rsync.gentoo.org/gentoo-portage"
USE="3dnow 3dnowext X a52 aac acl acpi alsa amd64 applet avahi bash-completion berkdb branding bzip2 cairo cddb cdinstall cdr cleartype cli consolekit cracklib crypt css cups cxx daap dbus djvu dri dts dvd dvdr dvi eds emboss encode evo exif fam fat ffmpeg firefox flac fortran fuse gdbm gdu gif glitz gnome gnome-keyring gpm gstreamer gtk hal iconv imagemagick java jpeg kdehiddenvisibility kpathsea latex lcms libnotify lyx lzma mad mikmod mmx mmxext mng modules mono mp3 mp4 mpeg mudflap multilib musicbrainz nautilus ncurses network network-cron nls nptl nptlonly ntfs nvidia ogg opengl openmp pam pango pch pcre pdf perl png policykit ppds pppd python qt3support qt4 readline reflection reiserfs scanner sdl session spell spl sse sse2 ssl ssse3 startup-notification svg sysfs t1lib tcpd threads tiff truetype unicode usb v4l2 vcd vorbis webkit x264 xattr xcb xinetd xml xmp xorg xpm xulrunner xv xvid zeroconf zlib" ALSA_CARDS="via82xx" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" ELIBC="glibc" INPUT_DEVICES="evdev" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LINGUAS="es es_ES en_US" RUBY_TARGETS="ruby18" USERLAND="GNU" VIDEO_CARDS="nvidia nv vesa" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account" 
Unset:  CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, FFLAGS, INSTALL_MASK, LC_ALL, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS


Reproducible: Always