sgasgar sgasgar # emerge -uDNav @installed

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild     U ~] x11-themes/gtk-engines-xfce-3.0.0-r200 [2.99.0-r200] USE="-debug" 0 kB
[ebuild     U ~] www-client/firefox-bin-12.0 [11.0] USE="-startup-notification" LINGUAS="ru -af -ak -ar -as -ast -be -bg -bn_BD -bn_IN -br -bs -ca -cs -csb -cy -da -de -el -en_GB -en_ZA -eo -es_AR -es_CL -es_ES -es_MX -et -eu -fa -fi -fr -fy_NL -ga_IE -gd -gl -gu_IN -he -hi_IN -hr -hu -hy_AM -id -is -it -ja -kk -kn -ko -ku -lg -lt -lv -mai -mk -ml -mr -nb_NO -nl -nn_NO -nso -or -pa_IN -pl -pt_BR -pt_PT -rm -ro -si -sk -sl -son -sq -sr -sv_SE -ta -ta_LK -te -th -tr -uk -vi -zh_CN -zh_TW -zu" 19,600 kB
[ebuild     U ~] xfce-base/libxfce4util-4.10.0 [4.8.2] USE="-debug" 421 kB
[ebuild     U ~] x11-libs/libwnck-2.31.0 [2.30.7] USE="introspection -doc -startup-notification" 617 kB
[ebuild     U ~] xfce-base/xfconf-4.10.0 [4.8.1] USE="-debug -perl" 506 kB
[ebuild     U ~] xfce-base/garcon-0.2.0 [0.1.9] USE="-debug" 422 kB
[ebuild     U ~] xfce-base/libxfce4ui-4.10.0 [4.8.1] USE="-debug -glade -startup-notification" 533 kB
[ebuild     U ~] xfce-base/exo-0.8.0 [0.6.2] USE="-debug (-python%)" 1,095 kB
[ebuild     U ~] xfce-base/xfce4-appfinder-4.10.0 [4.8.0] USE="-debug" 420 kB
[ebuild     U ~] xfce-base/xfwm4-4.10.0 [4.8.3] USE="xcomposite -debug -startup-notification" 1,075 kB
[ebuild     U ~] xfce-base/xfce4-panel-4.10.0 [4.8.6] USE="-debug" 1,012 kB
[ebuild     U ~] xfce-base/xfce4-session-4.10.0 [4.8.2] USE="consolekit policykit xscreensaver%* -debug -gnome-keyring -udev (-gnome%)" XFCE_PLUGINS="(-logout%*)" 1,228 kB
[ebuild     U ~] xfce-base/xfce4-settings-4.10.0 [4.8.3] USE="libnotify xklavier -debug -libcanberra" 765 kB
[ebuild     U ~] xfce-base/thunar-1.4.0 [1.2.3] USE="dbus exif libnotify pcre udev -debug -startup-notification -test" XFCE_PLUGINS="trash" 1,871 kB
[ebuild     U ~] xfce-base/xfdesktop-4.10.0 [4.8.3] USE="libnotify thunar -debug" 1,074 kB
[ebuild     U ~] xfce-base/xfce4-meta-4.10 [4.8] USE="svg -minimal (-session%*)" 0 kB
[blocks B      ] xfce-base/xfce-utils ("xfce-base/xfce-utils" is blocking xfce-base/xfce4-session-4.10.0, xfce-base/xfce4-appfinder-4.10.0, xfce-base/libxfce4ui-4.10.0)

Total: 16 packages (16 upgrades), Size of downloads: 30,632 kB
Conflict: 1 block (1 unsatisfied)

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

xfce-base/libxfce4util:0

  (xfce-base/libxfce4util-4.10.0::gentoo, ebuild scheduled for merge) pulled in by
    >=xfce-base/libxfce4util-4.10 required by (xfce-base/xfconf-4.10.0::gentoo, ebuild scheduled for merge)
    (and 9 more with the same problem)

  (xfce-base/libxfce4util-4.8.2::gentoo, installed) pulled in by
    =xfce-base/libxfce4util-4.8* required by (xfce-base/libxfcegui4-4.8.1::gentoo, installed)


It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously.  If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously. You may want to try a larger value of
the --backtrack option, such as --backtrack=30, in order to see if
that will solve this conflict automatically.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.